Performance Testing

Glenn E. Conatser1, Professor; Gordon Jones2, Professor; Ken Stalder1, Associate Professor

1University of Tennessee Department of Animal Science,

2Western Kentucky University Department of Agriculture


In The Beginning

The first recorded evidence of swine performance testing started in Denmark in 1907 and since then has operated continuously except for three years during World War I when a shortage of feed forced the suspension of all testing.  In those early days only swine bred at organized swine breeding centers were eligible for registration because those were the farms where breeders had complied with certain regulations including sending each year to the testing stations half as many litters as they had sows in their herd.  At the test station these test litters of four pigs each were fed under standard conditions.  The rate of gain and feed efficiency were recorded as well as carcass data.  “Advances made in the carcass traits (body length, belly and backfat thickness) plus efficiency of feed utilization were phenomenal.” (M.E. Ensminger, December 1942).


The first performance testing program that was used by U.S. pork producers was the production registry (P.R.) program initiated by the breed secretaries in 1938 through the National Association of Swine Records.  The program involved weighing litters of pigs at 56 days and recording the weights.  The information was sent to the breed associations and litters that met the minimum requirements were designated as P.R. litters.  A P.R. litter from a sow was one with eight or more pigs raised to a 56-day litter weight of at least 320 lbs. Or from a gilt (15 months of age or younger at farrowing time) with eight pigs or more raised to a 56-day litter weight of at least 275 pounds.  In other words, a litter of 8 pigs from a sow was required to average 40 pounds each at 56 days while pigs from gilt litters were required to weigh just over 34 pounds each at 56 days.


Table 1.   Duroc data for the first ten years of the Production Registry Program


Sows ++


No. of


Avg. no. farrowed

Avg. no. raised


avg. wt.

per pig

Avg. 56-day

litter wt.









































































*Duroc News - February 1949 (page 19)

**Gilt litters not included


In the first ten years of the Duroc program there were 7,672 litters weighed on the P.R. program, 4306 of these were sow litters (shown in Table 1) and 3366 were gilt litters (not included in Table 1).  Litters from sows averaged weighing just over 45 pounds more at 56 days then litters from gilts.  The top ranked Duroc sow in 1938 weaned 19 pigs that weighed 762 pounds at 56 days of age in two litters and was owned by Everett Thompson of Scheller, Illinois.  The top sow in 1939 weaned 20 pigs that weighed 868 pounds and was owned by Willard Waldo of DeWitt, Nebraska.


The first “production accredited” herd in the nation was the herd of The Louisiana State University in Baton Rouge, LA.  “Production accredited” honors were awarded to any herd that qualified 60% or more of all litters produced during a 12-month period of time.  John Beckett wrote in 1949 that “Production registry records will unquestionably pay biggest dividends to those breeders who keep records on the entire herd and farrowing season, rather than just a few occasional entries of selected individual sows.”  He continues “Complete herd records provide more valuable information to the owner for developing a constructive herd improvement program and naturally, carry more weight in the advertising program.”


The Production Registry (P.R.) program was sometimes called the Register of Merit (R.M.) program depending on the breed being tested and the breed association.  The rules were very similar but did vary somewhat on the number of pigs required to be weaned and the weight at 56 days.


A P.R. boar was a boar that had earned at least 15 points by having 15 daughters earn the P.R. rating.  A daughter would earn one point for each litter that qualified for the P.R. designation.  In 1949 the rules were relaxed to 10 points on the basis of daughters for the P.R. boar designation in order for more boars to quality on their first pig crop.  “In making this change, the swine breed secretaries were fully aware of the fact that the number of P.R. litters sired is not as accurate a measure of a boar’s breeding worth as the number of his daughters that raise P.R. qualified litters.”  However, provision was made for a definite distinction between the two.  On the basis of litters sired, a boar was called a “P.R. boar,” but on the basis of daughters he was known as a “star P.R. boar” for one unit of daughters, a “two star P.R. boar” for two units of daughters, etc.  The “star” naturally denoted a higher honor.  A “unit” was any combination of ten P.R. litters.  A boar was given additional stars for each unit of ten P.R. litters from his daughters.  A P.R. rating from siring P.R. litters required 15 litters to qualify the boar.


Ton Litters

Around 1944 a second performance program was started.  This was the ton litter program initiated by the Duroc association.  This program was very popular with breeders

and required that producers enter the litter with the breed association giving the number of pigs in the litter within 15 days of farrowing.  This litter information had to be verified by an FFA or 4-H advisor, a county agent, an AAA committeeman, a cow tester, a veterinarian or “some other person with public responsibility.”  The litters had to be weighed at 180 days (plus or minus 10) and the weight report sent to the breed association within five days of the weighing.  Weighing had to be verified by one of the officials mentioned above.  In the first five years of the program there were 577 ton litters in the Duroc breed.  (Duroc News Journal, January, 1949)


How About a Fair Deal for Pork and Lard - The Beginning of a Focus on Lean Production


In an editorial in the Duroc News dated February of 1949, Mr. Bing Evans, Executive Secretary of the Duroc Association, asks the question “What about pork and lard?”  He states that lard is and has been a drag on the market for some time, but only small quantities have been exported through land-lease or the Marshall plan.  He says, “With lard selling for about half the market price of just one year earlier, what more substantial food, dollar for dollar invested could they ship to Europe?”  He asks all breeders to contact their elected representatives and put pressure on them to increase the exports of lard.


In another article in July of 1949, Mr. R.G. Plager, of the John Morrell Company, talks about solving the lard problem.  He states that when a group of hog producers get together it doesn’t take long for someone to raise the question, what has happened to the lard market and what can be done about it?  He says the price of any product declines when the supply exceeds the demand, and that in simple terms is what happened to the lard market.  The factor that concerned pork producers in 1949 was that lard was selling at wholesale for about half the price of live hogs.  During the period 1910-1919, the wholesale price of lard averaged $4.46 per hundred pounds above the price of live hogs.  This price had gradually declined until March of 1949 when lard averaged $7.26 less than the price of live hogs.  Mr. Plager offered three suggestions to solve the problem.  The first was to produce a more intermediate type hog, one that was not so short and fat and one that was not tall and narrow.  Second was to market hogs at a lighter weight of 180 to 240 pounds.  He states that a 300 pound slaughter hog produces more lard than two hogs weighing 200 pounds each.  The third suggestion was to improve the quality of lard to compete with the new vegetable oils and to advertise the new lard as being a better product.  It was becoming obvious that lard was on its way out as a product wanted by the American housewife.


What is the Best Type?

William J. Loeffel, chairman of the Animal Science Department at the University of Nebraska, raised this question in 1949.  According to Loeffel, type is constantly changing with changes in economic conditions. For example, the mechanization of industry and agriculture has sharply reduced the demand for fat meat cuts and lard, once regarded as essential in the working man’s diet.  This caused the development of the meat type hog at the expense of the lard type hog.


At the end of 1951 the Duroc Association had tested 144,444 purebred Duroc litters on their P.R. program.  At this point the difference between average litter weights of sow and gilt litters had grown to 54 pounds per litter.


Wisconsin Hogmen Increase Profits Through Swine Selection Coop

The Wisconsin Swine Selection Cooperative had its origin back in 1945 when 30 hog producers got together with professor James Lacey and Dr. A.B. Chapman, Professor of Genetics at the University of Wisconsin, and organized the group.  “The improvement program was based upon the premise that individual pigs and litters differ greatly in the inheritance they carry for litter size, vigor, livability and rate of gain, and that all of these factors are more or less heritable.”  The program was directed toward enabling the swine producer to make his selections from the top of the herd when he is selecting breeding gilts and boars for next year’s crop.  As a yardstick for measuring efficiency of pork production, the Wisconsin cooperative used an index that could be readily computed from simple records kept by the producer.  The index was based on size of litter farrowed, size of litter weaned, weight of litter and weight of the individual pigs at five months.  One point was allowed for each pig farrowed, two points were given for each pig raised to five months, total litter weight at five months was divided by 100  and 0.7 point was given for each pound over 75 for the individual pig at five months.  The average index for the Wisconsin program in 1948 was 90.  The index for the top 25% of herds was 127 and 59 for the low 25%.  Extension Specialist, D.H. Williams, states that the pig indexes are most valuable when used to compare pigs on the same farm.  The project was set up as an improvement program, not a contest.  All litters on the farm were enrolled, not just the promising ones.  The only comparisons made between farms was in the form of a herd analysis sheet prepared each fall when the index sheets were returned to herd owners.  The analysis gave state averages and in addition, gave each member a personal report on his own averages.  According to D.H. Williams, the program was designed to increase litter size by selecting only gilts from large litters, increase growth rate, improve mothering ability of sows and to eliminate genetic defects such as hernias and inverted nipples by selecting only sound pigs from sound litters.  All of the pigs in the program were identified by ear notches and all of the weighing was done by a coop fieldman and the local county agent.


General policy in the operation of the cooperative was directed by the purebred and commercial swine producers who represented different parts of the state.  A lifetime membership in the swine improvement coop was $2.00.  There was a service charge for each litter weighed graduating down to 50¢ per litter when there were 20 litters to weigh.  In the course of his routine calls upon members, the coop fieldman would check litter record cards at farrowing time to be sure they were complete and accurate, including ear notches.


Crossbreeding or Disease Control?

In an editorial dated February, 1952, Bing Evans, secretary of the Duroc Association, raised the question about crossbred and hybrid hogs and swine diseases.  He says “Recent public criticism of a corn belt state college for it’s apparent friendliness toward a so-called hybrid hog company has stirred up plenty of comment.  Especially since a part owner of this company is connected with the state board of education.  The complaint was signed by all officials of the state purebred associations except one, and he is employed by the college.”  He continues that “They were somewhat aggravated as taxpayers for the vast amount of publicity cranked out regarding the success of these crossbreeding experiments which a few colleges are and have been generating for some years without conclusive proof of producing a hog of ultra efficiency or one that’s any better than good purebreds.”  “While all of this vast program of crossbreeding has been going on for years through the USDA and some agricultural colleges connected with the program, swine diseases have gained ground tremendously.  Millions of pork producers dollars have been lost through cholera, erysipelas, influenza, dysentery, baby pig disease, TB and the devastating new disease that has swept hog herds recently, atrophic rhinitis.”  He continues “It is easy to find fault we know, but our criticism is constructive when we raise the question: Would these various diseases now be under control if some of the millions of dollars spent on crossbreeding programs had been invested in disease research and control?”


Too Much Fat Says OPS

In 1952 the office of price stabilization charged packers with violating the law by selling pork with too much fat on it.  Millions of dollars were reported to be involved.  The trouble started when packers reportedly sold pork loins with layers of fat from 1 ½ to 2 ½ inches thick, while OPS regulations limited the fat to ½ inch.  The OPS began investigating after the retailers complained that they were forced to cut off the fat before housewives would buy the cuts.  OPS reported in one case where a retailer trimmed 100 pounds of fat from a 500 pound shipment of pork loins.  An editor’s note on the fat problem is interesting.  The editor notes that as long as farmers continue to feed hogs as they do, (any type or any breed) by pushing in a lot of corn for finishing, there will be lots of lard.  He notes that “Until there is a large enough price differential between lean and fat hogs to make it economical for farmers to finish them properly, fat hogs will keep coming to market.”  He then asks the question “what should be done?”  He states further that the customer has the money to buy meat, but he doesn’t like too much fat on his pork.  Then he suggests that the simple answer is to just trim off the fat!  There was no mention of the possibility of breeding to attain leaner hogs.


By the early 1950's it became obvious that fat and lard were the reasons pork consumption was taking a beating and the price of live hogs was in the high teens and low twenties .  Lard was a commodity with very little value and hogs were fat without much muscle.  In 1952, the average price paid for hogs was $18.13 and the price of corn was approximately $1.65 per bushel.  The hog/corn ratio was 11.  In an editorial in the Yorkshire Journal, it states that “after years of clamoring for it, the day of the meat type hog seems to have arrived.  It is the talk of the stock yards, of the packers, of purebred men and everyone else in the industry.” Carcass contests were started, first at the National Barrow Show and at the International Livestock Show.  At the International Dressed Carcass contest in 1952, the Yorkshire breed won all divisions, grand and reserve champion and had more winners than all other breeds combined.  The Ohio State University, Michigan State and Purdue were entering Berkshires in the carcass contests and doing relatively well.  The name of Oscar Anderson began to show up regularly as being competitive in carcass shows with Poland Chinas.


In the state of Ohio, under the sponsorship of the Ohio State Extension Service and other interested parties, a performance program was developed where litters could be “certified” on the basis of number of pigs born, rate of gain, economy of gain and carcass value.  This program was developed around 1947 and was similar to the Wisconsin program except that the Ohio certified program had a carcass component.


The “production accredited” program that became a part of the P.R. testing procedure was awarded to five producers in 1951.  “Production accredited” was an honor given to herds that qualified for P.R. 60 percent or more of all litters raised during the year.  The top herd was Fred Ottinger of Elgin, Illinois with 94% of his litters and second was W.H. Waldo of DeWitt, Nebraska with 75.6% of his litters meeting the P.R. standards.


In an article in the Duroc News in July of 1952, Mr. Waldo states that the P.R. program helps recognize outstanding herds but it’s greatest value is in singling out the best producers within a herd.  He says it is more difficult to compare records of one herd with another where environment may vary considerably and have more influence on the records than the heredity of the animals.  Even so, he says, P.R. helps breeders locate high producing breeding animals and it has proved to be a valuable guide to commercial men.


USDA Adopts New Grade Standards

The USDA adopted grade standards for slaughter barrows and gilts in September of 1952:  Choice No. 1 - slaughter hogs with about the minimum finish required to produce high quality pork cuts.  Carcasses have a relatively high ratio of lean to fat and usually yield about 50 percent of their carcass weight in the four lean cuts of hams, loins, picnics and boston butts.  Choice No. 2 - slaughter hogs producing high quality pork but decidedly overfat.  Carcasses yield a somewhat low proportion of lean cuts and a high proportion of fat.  These carcasses normally yield less than 45 percent of their weight in the four lean cuts.  Medium - slaughter hogs are slightly under finished and as a result produce flabby and slightly soft cuts with little marbling.  These cuts are of medium quality.  The yield of lean cuts is proportionately high but the ratio of total lean and fat to bone is slightly low.  Cull - hogs of this grade are decidedly under finished, and although they produce carcasses with a high ratio or lean to fat, the cuts are very inferior in quality and are suitable only for use in processed meats.


The grades which were the results of several years of research, will supplement present tentative standards for live hogs and establish for the first time standards for pork carcasses (USDA, 1952).  The new grades were to be used on a voluntary basis by producers, livestock, market men, packers and others.


Inbred Strains Valuable

In an editorial in the Duroc News in October, 1952, editor Bing Evans stated that professors L.N. Hazel and Dr. J.L. Lush of Iowa State College were “appealing to breeders of purebreds to develop inbred strains within each breed in order to facilitate the work of swine breeding at the various state colleges in ten years.  The Iowa College has championed the fact that by crossing two inbred lines within the same breed, hybrid vigor can be obtained.” 


In November of 1952 the Duroc Association made the announcement that because of the IBM system for recording hogs used by them, that it is now possible to uncover interesting figures that would otherwise be difficult or impossible to find.  They reported that in 1951 there were 47,872 litters of purebred Durocs raised and that the average litter size farrowed was more than ten pigs.  There were eight pigs raised per litter to weaning age.  They also reported that in 1952 there were 135 ton litters recorded.  The average litter weight at 180 days was 2450.3 pounds, they had an average 56 day litter weight of 408.49 pounds and the average number of pigs in the ton litters was 10.7.  The top ton litter weighed 3715 pounds at 180 days and was owned by Clarence Chappell, Jr. of Belvidere, North Carolina.


Certified Superior Hogs are Coming

On April 7, 1953, the swine breed secretaries and a number of interested representatives of the swine industry met at Purdue University in Lafayette, Indiana to discuss plans for formulating a program of identifying superior strains of efficient top quality carcass yielding hogs and recognizing them officially.  The meeting had been called by Bob Shannon, secretary of the Yorkshire Association and president of the National Association of Swine Records.  Others attending were Claude Mitchell, Poland China Record Association, Willard Brittin, American Berkshire Association, Levi Moore and Pat Lybrook of the Chester White Record Association, Rollie Pemberton and Harold Boucher of the Hampshire Swine Registry, F.G. Ketner, Ohio Cooperative Producers Association, Bernard Ebbing, Rath Packing Company, Wilbur Plager, secretary of the Iowa Swine Producers Association and Claude Harper, head of the Animal Husbandry Department, Purdue University.


It was pointed out, in the discussion, that “there is a definite need for a program of buying hogs based on merit.  That to make such a program more workable, there is a need for more hogs meeting desirable carcass qualities.”  There was clear evidence that there were strains of hogs that will reproduce uniform market hogs of desirable type.  They concluded that “a program to help identify and certify these superior producing strains could be one of the most constructive developments in the history of the swine industry.”  A committee was appointed to prepare standard requirements for certification.  The committee consisted of Rollie Pemberton, Wilbur Plager, Bernard Ebbing, Larry Kunkle and Carroll Plager.


It didn’t take the committee long to formulate the first standards for what was called the Three Point Certification Program.


            1.  Requirements for “Certified Litter”



         1)  In view of the widespread discussion of possible changes in the age of                                        weighing P.R. litters it was decided to set up temporary requirements as


   a)    No fewer than 8 pigs to be weighed at 35 or 56 days of age

b)        The age of weighing and the minimum weight of 35 days of age shall be whatever is called for in the standard rules for P.R. in the breed               involved

    c)    For those using the 56-day weight the minimum weight shall be:

1)     Dam 15 months or under at farrowing-275 lbs.

2)     Dam over 15 months of age at farrowing-320 lbs.

2)  Litters failing to meet these requirements may go no further.



1)  The weight shall be the “off truck” weight

2)  The minimum weight for age shall be 200 lbs at 180 days or the

                             equivalent plus or minus for each day over or under 180 days.                          

3)  Weight limits for pigs submitted for slaughter:

a)     Maximum weight shall be 230 lbs.

b)        Minimum weight shall be 180 lbs.

                        4)  Pigs shall be tattooed by slaughterer when weighed



1)   Maximum and minimum carcass lengths, based on average of two pigs.

                              (Measurements to be taken from the front of the first rib where it joins

                              the vertebra, to the front of the aitch bone.

a)     Live weight from 180 lbs. to 199 lbs. inclusive, 28.5 - 31.5          


b)        Live weight from 200 lbs. to 214 lbs. inclusive, 29.0 - 32.0 inches

c)        Live weight from 215 lbs. to 230 lbs. inclusive, 29.5 - 32.5 inches

2)         Maximum and minimum fat back thickness - average of two pigs

                                    a)     Thickness to be measured at three points as follows:

1)  Opposite third thoraic vertebra.)     

2)  Opposite last thoraic vertebra.)                    Average of these

3)  Opposite last lumbar vertebra.)                    three measurements

b)     The maximum and minimum shall be as follows:

1)  Live weight from 180 lbs. to 199 lbs. inclusive,

     1.1 to 1.6 inches

2)  Live weight from 200 lbs. to 214 lbs. inclusive,

     1.2 to 1.7 inches

3)  Live weight from 215 lbs. to 230 lbs. inclusive,

     1.3 to 1.8 inches.

  c)     The measurements are to be taken from the tip of the spinal

                                               process to the outside of the skin.

  3)         Minimum area of lean loin, based on average of two pigs.

  a)       Loin is to be broken at the 10th rib and tracing of lean rib eye area

                                                taken on parchment paper

  b)       Loin muscle area required by compensating planimeter               


1)       Liveweight from 180 lbs to 199 lbs. inclusive, 3.5 square inches

2)       Liveweight from 200 lbs. to 214 lbs. inclusive, 3.75 square inches

3)       Liveweight from 215 lbs. to 230 lbs. inclusive, 4.00 square inches


“Certified Litter”

1.         A litter that has met the above requirements is a “certified” litter.

2.         A litter from a repeat mating of one that has met the requirements is a

                        “certified” mating.

3.         Suitable identification shall be put on the registry certificates of all pigs from

                        “certified litters’ and “certified matings.”


“Proven Sire”

A “proven sire” is one that has sired five litters that qualify as “certified” litters.  These litters must be out of five different sows, not more than two of which are full sisters or dam and daughter.  The registry certificates of such boars shall bear suitable identification - probably by the addition of P to their registry number.


Probably Operation

1.         The BREEDER                        a) Qualify litter in Production Registry

                                                            b) Present two pigs from the litter for slaughter

    when weighing between 180 lbs. and 230 lbs.


2.         The SLAUGHTERER            a) Weigh pigs submitted when unloaded

                                                            b) Tattoo pigs for identification

                                                            c)  Kill and stamp loin in accordance with tattoo


d) Make called for measurements and trace lean

                                                                 area of loin on parchment paper provided

                                                                 for purpose.

                                                            e)  Enter measurements on report form, sign and

                                                                 mail with loin tracing to breed office or college.




            a) Give moral support and encouragement to program

            b) Recommend and instruct slaughterers

            c) Occasionally spot check work of slaughterers

            d) Determine area on tracing with compensating planimeter

            e) Check figures and averages of measurements given on form

             f) Cooperate with breed offices in seeing that the program is properly conducted


The certification program was up and running but some breeds were slow to adopt it.  The Hampshire breed was the first to try it at a national type conference in 1954, and only one litter met the requirements out of several that were entered.    The Duroc breed was next to try it and none of the 30 litters entered met the certification standards.


Swine Breeding Research - Quality Pork Becoming Important

In an article in the Hampshire Herdsman in June of 1953, Dr. L.N. Hazel of Iowa State College stated that  “present day techniques provide a challenge to the swine industry to develop systems of swine breeding research useable to all swine producers.”  He said that “the response of the industry may well determine whether the pig continues to be the mortgage lifters of the corn belt.”  Hazel said “let’s face it, pork has already gone a long way toward acquiring a reputation as a low quality product.  We hear a great deal about the lard problem, because surplus lard is a physical and tangible thing which can be seen and measured.”  However, he says that consumer acceptance of pork is more important than a lard surplus.  He says, “we realize this more and more as competition from the growing beef and broiler industry make themselves felt.”  Much still is not known about quality in pork, but it is obvious that the most important detriment of the kind we have now is over fatness.”  Over fat hogs, he says, produce too much lard as well as low quality meat.  Hazel points to research by Dr. Joe Kastelic and Ed Kline to show the differences in three types of hog carcasses.


Table 2.  Percentage of Fat in Three Types of Hog Carcasses



Closely Trimmed

Wholesale Cuts


of Hog



























By contrast, Dr. Hazel points to the Danish system of improvement.


Table 3.  Changes in Danish Pigs Between 1924 and 1948








Daily Gain (lbs.)



Feed required per lb. Gain



Length (inches)



Back Fat (inch)



Belly (inch)




The Swine Improvement Association of Ohio opened their swine testing station to accept pigs farrowed in the fall of 1954.  The station could accommodate 108 pairs of littermates.  All litters had to meet P.R. standards and in addition, a pair of littermates had to be delivered to the test facility on or before the day they were 60 days of age.  A barrow and gilt were preferred, but two barrows or two gilts were acceptable.  Pigs were slaughtered at approximately 210 pounds at the Ohio State University meats laboratory.  The carcass value was measured by the percentage of live weights found in the four primal cuts, skinned ham, trimmed loin, trimmed belly and New York shoulder.  A primal cut yield of 49 percent or over was called a certified Ohio Improved Record.    In the beginning the cost to the producer was one pig given to the University and the University would purchase the other pigs on a formula basis.


USDA Announces New Backfat Probe

On June 30, 1954 Mr. Ralph Durham of the USDA announced a new method of measuring backfat on a live hog.  A method was developed whereby a very small incision was made through the skin and a small measuring ruler about one quarter of an inch wide was inserted through the opening of the skin.  The ruler was pushed downward through the opening in the skin and pushed downward through external fat until lean muscle was touched.  The thickness of the backfat was then measured to the tenth of an inch on the ruler.  According to the USDA, in the past (prior to 1954) it had been necessary to slaughter the animal to determine the amount of “lean meat produced”.  With this new probing technique, performed when live breeding animals were near market weight, the meatier individuals could be determined.


The USDA announcement was a result of research conducted at Iowa State College in the fall and winter of 1950-51 by L.N.  Hazel and E.A. Kline (1952).  They developed the procedure using 96 hogs that were measured using the new procedure and comparing the results with carcass measurements taken on the same hogs.  The correlation between the average of four backfat measurements taken on carcasses and on live hogs was .81.  Measurement made on the 96 live hogs were slightly more accurate as indicators of leanness and percent primal cuts than were carcass measurements of backfat thickness.  The most accurate locations were just behind the shoulder and at the middle of the loin about 1 ½ inches off the midline of the body (Hazel and Kline, 1952).  The use of this simple technique was one of the most important steps in the change from fat hogs to meat type hogs in the 1950s and later.


Hampshires Lead the Way in Certification

Without question, the Hampshire Association led the way in the early years of the certification program.  The Hampshire breed secretary, Rollie Pemberton, led the charge and gave the program much publicity in the Hampshire Herdsman magazine.  The first certified litter in America was owned by Dean Snyder of Good Hope, Illinois.  The litter was sired by King Edward P.R. 93 and the carcass data was gathered at the Oscar Mayer Packing Company in Madison, Wisconsin during the 1954 Hampshire Type Conference.  Five litters were entered in the type conference class set up for certified litters.  Only one litter certified and those that failed were due to being too short or not having enough loineye.  None failed because of backfat.  King Edward was recognized as the first certified meat sire of any breed.  The first certified litter was slaughtered at 210 and 214 pounds, had 29.25 and 29.6 inches of body length, 1.3 and 1.4 inches of backfat, and loineyes of 4.43 and 4.17 square inches, respectively. 


The industry leader who had, without a doubt, the biggest impact on the certification program was Carroll Plager of George A. Hormel and Co.  He gave leadership to the development of the program and was among the first to purchase hogs on the basis of carcass merit.  Others who were influential were his brothers Wilbur Plager, secretary of Iowa’s Swine Producers Association and later secretary of the Yorkshire breed association, R.G. Plager of the John Morrell Company and Bernard Ebbing of the Rath Packing Company.  Colleges and Universities that gave leadership to the early certification program were Ohio State, Purdue, Cornell, Oklahoma A & M, Michigan State, University of Wisconsin, University of Tennessee, Iowa State, Fresno State, Texas A & M, LSU and Washington State University.


In a Hampshire Herdsman editorial, Rollie Pemberton says “it is paramount that our leaders keep in mind the fact that we producers in the cornbelt are going to feed our corn to these hogs so the quicker we breed more meat into these practical hogs, the better off everyone identified with the industry will be.”


Early Weaning - Not a New Idea

Aside from performance testing, several other noteworthy articles were discovered while doing the research for this article. One of those was an article by Damon Catron of Iowa State College in 1954 concerning early weaning of pigs.  Catron stated that feeding pre-starter plays a big part in the early weaning of pigs.  He says, “pigs may be weaned from sows at 7 to 14 days of age or at the earliest when they reach a weight of five pounds”.  He continues “that most experienced producers may find it best to wait until pigs weigh 8 to 10 pounds before weaning under farm condition.  Weaning depends on adequacy of housing and equipment, facilities for keeping pigs warm, disease level and skill of management.”


New Electric Backfat Probe

At the November 26, 1954 meeting of the American Society of Animal production in Chicago.  Dr. R.M. Whaley of the Purdue University Physics Department and Dr. F.N. Andrews of the Animal Husbandry Department announced that they had invented a new tool to accurately measure the thickness of backfat on live hogs and carcasses.  The device was manufactured by Duncan Electric in Lafayette, Indiana and was sold by most of the breed associations for $82 each.  It was called a Lean Meter. 


Iowa Makes Plans for Pig Testing

In early 1955, Dr. L. N. Hazel of Iowa State College proposed a plan for building a swine testing facility in Iowa.  He said that “it seemed desirable at this early stage to test both boars and barrows of similar breeding so that live-hog methods of evaluation can be compared with actual carcass measurements”.  He said that “if the correlation is high, the testing of barrows can be discontinued as experience and confidence are gained in live hog methods.: The choice of testing six pigs by the same sire but out of at least three litters is based on the following consideration:


1)  It seems to be an optimum compromise between adequate testing and the number of    

     pens which can be tested.


2)  It permits the testing of four boar pigs directly which can be used as herd sires 

     immediately if they are sufficiently productive.


            3)  It provides carcass evaluation on two barrows after slaughter.


            4)  It provides a reasonably accurate progeny test of the breeder’s herd sire.


5)  It provides reasonably accurate family information on the untested brothers and sisters      

     of the test lot of six pigs.


6)      The six pigs from each sire are to be divided equally into two pens, so that the      

     difference between two pens provides a measure of the sampling variation involved.


Hog Men Forming National Council

At the National Barrow Show in Austin, Minnesota in September of 1954 a committee of hog men met and called itself the organizational committee of the National Swine Growers Council.  Arrangements were made for a final organizational meeting to take place in Chicago during one of the days of the International Livestock Show.  Temporary Chairman of the organization, named at the Austin meeting, was Wilbur Plager, secretary of the Iowa Hog Producers Association.  He was directed to invite delegations from each corn belt state to the meeting in Chicago.  The committee asked that each delegation should include at least one commercial producer.  Attending the Austin meeting were Charles Maas, Evansville, Wisconsin; Harry Russell, University of Illinois; Bob Parkinson, Francesville, Indiana; Clarence Myers, Blue Earth, Minnesota, President of the Minnesota Swine Producers Association; Marion Steddom, Grainger, Iowa, President of the Iowa Swine Producers Association; Keith Myers, Grundy


Center, Iowa; Richard Wilson, Ohio State University; C.W. Mitchell, Secretary of the National Association of Swine Records; and Wilbur Plager.  These men probably had no idea at the time that they in fact were forming what is now known at the National Pork Producers Council.


In June of 1955, Dr. J.C. Hillier of Oklahoma A & M College summarized the first year data from the Hampshire Certification Program.


Table 4.  Average Measurement in Weight Classes*


Liveweight Range




Number of hogs




Average weight




Average age (days)




Average daily gain (from birth)




Average length




Average backfat thickness




Average loin area (sq. inches)




*Hampshire Herdsman (June, 1955)


There were 242 head of Hampshire pigs slaughtered in the certification program during the first year and 45% of them met the standards for certification.  Of those that failed to certify, the main reason was weight for age followed by loin eye area and backfat.


The second year summary prepared by Dr. Hillier showed an amazing increase in Hampshire breeders participating in the certification program.  There were 973 head slaughtered the first and second year with 376 of them meeting certification standards.


Table 5.   Summary of measurements on 973 Head of Hampshires*


Wt. Class Pounds

No. Head

Avg. Slaughter Weight

Avg. Age

Avg. Daily Gain

Avg. wt. @ 180 days

Avg. Length

Avg. Backfat

Avg. Loin eye size




























Sum or Average









*Hampshire Herdsman (June 1956)



Merit Buying of Hogs Recommended by Meat Institute

Trade Association Urges Immediate Adoption of a More Selective Systemof Hog Buying


Immediate adoption of a more selective system of buying hogs on a nationwide scale has been recommended by the American Meat Institute.  The institute, national trade association of the meat packing industry, said it bases the recommendation upon the “clearly outlined desire of the top executive of every food industry - Mrs. American Homemaker.”


“In recent years, this lady has demonstrated a decided preference for leaner pork,” the Institute points out.  “This pork is best produced from the so-called meat type hog.  The Institute’s members feel that the adoption of a more selective buying system will lend encouragement to the increased production of pork tailored to meet today’s appetite demands. 


“Producers will benefit in two ways.  It is cheaper to raise meat-type hogs than their fatter cousins.  In addition, and most important for the future of the nation’s hog-corn economy, more lean cuts in the total pork supply will improve consumer demand for pork.”


Recognizing these facts, meat packing companies have been attempting to purchase hogs on a “merit basis,” a basis which recognizes value difference between individual hogs in their offering prices.  It is hoped that the Institute’s recommendation eventually will expand this system to a nationwide scale in every market. In order for packers to be in a position to offer separate price quotations for hogs of different value, it was pointed out that the hogs have to be sorted for both weight and grade before they are offered for sale by producers or their marketing agencies. Hog producers frequently point out that they have not received sufficient price incentive to adjust their production to meet consumer demand.  The Institute stated that this price problem is not simply a matter of “paying premium” for meat-type hogs.  Packers cannot pay more for desirable hogs unless discounts for the less desirable, over-fat hogs are incorporated in their buying practices at the same time. 


“Pricing of hogs should not be looked on as a matter of premiums and discounts at all,” according to the Institute.  “Merit buying is more properly described as a system in which value differences for individual hogs, based on both weight and quality, are recognized by both buyer and seller.  Each should realize that the value of any hog is determined by how much the products from that hog will bring when sold.”


The historical practice has been for hogs to be bought and sold by lots or droves.  This system gives broad recognition to weight differences.  Differences in grade, which depend largely upon the relative lean-fat ratio of the hog, have been largely overlooked.  Such differences in grades were not important so long as the hog industry enjoyed a strong export market for lard, and American consumers expressed no strong dislike for excessive fat in the pork cuts.


This situation now has changed greatly and there are actual value differences between individual hogs in today’s market depending not only on weight but grade as well.  As a result, the meat packing industry, through the Institute, has cooperated extensively with leading farm organizations, hog breed associations, college and university people, marketing agencies and others interested in stimulating greater interest in meat-type hogs.


This effort already has resulted in significant progress.  Two years ago, only one hog out of ten was tailored to meet consumer demand.  Last year, one out of six met the meat-type hog requirements.


“This shift in the type of hogs being raised and in the degree of finish at which hogs are marketed is encouraging,” the Institute believes.  “It indicates that producers are aware of present-day market trends.  They are taking steps to adjust their production practices to meet the demands of the buyers of their products.”


In 1955, the meat packing industry made a big step forward on its own in this area.  The Institute recommended that new closer trim of fat on pork cuts be adopted, and this recommendation is now in wide use.  This results in an important exterior improvement in the product, but it does not do the full job of enhancing the attractiveness of pork cuts in the retail meat case.  Closer trimming cannot correct excessive internal fat, or improve skimpy muscling in hogs not coming up to meat-type requirements.  These two quality factors are determined solely by the type of hogs which farmers raise and market.


“The expansion of meat-type hog production, stimulated by the newly recommended merit buying policies, will add up to one of the most important factors that will keep America’s hog economy on sound and improving basis.  By ‘giving the lady what she wants,’ it is hoped that this cooperative effort will keep pork where it belongs - high in consumer demand and flavor,” the Institute concludes.


In the mid to late 1950's almost every hog producing state built a swine testing facility.  Some of these tested only boars and some only tested littermate barrows and gilts.  Some of the earlier ones not already mentioned were in McLean County, Illinois at the stockyards in Bloomington, Michigan State University in East Lansing, South Dakota State University at Brookings, Western Illinois University at Macomb, Minnesota swine testing stations at Austin and New Ulm, University of Missouri at Columbia and others.


On-farm Testing program Initiated by Duroc Breed

According to the Duroc News in May of 1959 “testing is the thing.”  They say “a hog is nothing these days unless he has been tested.”  The new on-farm “Superior Meat Sire” (SMS) program added rate of gain and feed conversion records to the P.R. and certification programs.  The offspring of a sire could be placed on test on the farm if 50% or more of his litters had qualified for production registry in that farrowing season under the breeds production registry herd test program.  Fifteen or more barrows and gilts out of at least five different litters by the eligible sire could be placed on rate of gain and feed efficiency test when they were from 35 to 60 days of age.  Two-thirds or more of the pigs placed on test had to be submitted for slaughter at an approved slaughter facility.  At least five different litters had to be represented in the slaughter group.  The regular carcass measurements for certification were taken by the slaughter facility and reported to the breed association.  If ten or more head submitted for slaughter averaged:  29 or more inches in carcass length, 1.5 inches or less in backfat, and 4 or more square inches of loin eye area, then the sire met the minimal carcass requirements for the SMS program.


Additionally, if the test lot reached an average weight of 200 lbs. or more by 165 days, and had a feed efficiency of 3.20 or less, the sire would be designated a SMS SIRE.  A super meat litter was a litter that met all of the qualifications for a certified litter and in addition two or more pigs had been fed out in an on-farm testing program and had met the requirements for growth rate and feed efficiency.  A boar was recognized as a superior meat type sire when he had sired five superior meat litters or when he had qualified under the on-farm testing program. A boar was called a “Superior Certified Meat Sire” if all of the individual pigs met the minimum certification requirements.


The certification program was adapted by all of the breed associations, of course, some of the breeds processed many more records than the others. The Hampshire and Duroc breeds, and to a lesser degree, the Yorkshire and Poland breeds adapted the program and encouraged their breeders to participate.  The following table summarizes the Hampshire data from the fall of 1955 through April of 1959


Table 6.  Hampshire Swine Registry Certification Data Summary

                      Summary of Measurements on 6349 head of Hampshire Pigs tested through April 30, 1959


No. Head

Weight Class


Slaughter Wt.

Avg. Age


Daily Gain

Avg. weight at 180 days

Avg. Length

Avg. Backfat


Loin Eye





























Sum or avg.








Hampshire Herdsman - July 1959


In early 1960, the certification standards were changed.  All hogs had to be slaughtered at 220 pounds or less and had to reach 200 pounds in 180 days or less.  All carcasses had to have at least a four inch loin eye regardless of weight.  Backfat had to be less than 1.6 and length had to be 29 inches or more.        Additional changes were made in 1963 when 12 or more head had to be slaughtered, average backfat had to be 1.5 or less and length had to be 29.25 or more.  Average loineye had to be 4.25 square inches or more.  A superior certified meat sire was one that had 12 or more offspring meet certification standards.  At this point in the program (1963) the standards for the Hampshire, Duroc and Poland breeds were identical.  In 1962, the Duroc breed had 248 certified litters from 71 breeders in 22 states.


Table 7.  Certification Data from 2600 Barrows and Gilts

                                                                                            Duroc – 1962


Average number of pigs raised


Actual weight

203.5 lbs.

Days to 200 lbs.


Carcass length


Average Backfat


Average Loineye


The Duroc News - February 1963


Ultrasound Instrument Gives Accurate Carcass Estimate

In late 1965, L.H. Hazel of Iowa State University announced the development of sonoray techniques for estimating composition in live hogs with a high degree of accuracy. Hazel said that earlier sonoray methods were no more accurate than a backfat probe for evaluating pigs.  With the new method, there was a correlation of .9 between the ulltrsonic measurements and the actual percent lean and loin in the carcass.


In the late 1960's, certification standards continued to change.  In 1968, the maximum backfat was lowered to 1.5 inches and the days to 200 pounds was lowered to 170, carcass length stayed at 29 inches and loineye requirements remained at four square inches.  The 1963 standard of 4.25 square inches.


In 1968 , the Duroc breed listed the breeders that had certified the most litters since the inception of the program in 1956.  The leading breeder was Stro-Wold Farms in Bowling Green, Missouri with 211 litters and second was Forkners CC Farms of Horton, Missouri with 136 litters.  There were Iowa State University, The University of California at Davis and the University of Tennessee each with 42 litters certified.


The first Superior Certified meat sire in the Duroc breed was CC Long Trend, owned by Forkners CC Farms of Horton, Missouri.  CC Long Trend was bred by Henry Krivohlavek and son of Dorchester, Nebraska.  He was purchased by Forkner farms in 1963 at the Southwestern Type Conference.  The second SCMS sire was Royal Challenger owned by H.G. Lorenz of Lubbock, Texas.


Professor E.R. Lidvall of the University of Tennessee wrote a yearly article in the Duroc News starting in 1964 on the pedigree analysis of tested Duroc sires.  It was a summary of bloodlines that were influential in the certification program.  In 1964 he wrote that “testing information is a must for the successful swine breeder.  It is not a new story anymore that commercial raisers are demanding and paying a premium price for those boars backed by test information.”  He says that “numerous tools are available to the constructive breeder to do this important job.  Breed improvement programs such as P.R. and certification including both CMS and SMS programs, swine testing and evaluation stations, the show ring, barrow shows and carcass contests can all be used to produce a better hog.”  Professor Lidvall found that in the Duroc breed the Buster Boy family was the most influential during the early years of the certification program.  Fifty nine percent of all CMS and SMS sires in the first 146 that were recognized were from the Buster Boy line.  Buster Boy himself was somewhat of an unknown boar but he left two important and influential sons in Defender and Crimson Flash.


The first certified meat sire in the Yorkshire breed was Garlick British KD.  He was bred by Russell Garlick of Winnebago, Minnesota.  By August of 1967, there were 214 CMS boars in the Yorkshire breed.  At this point in the certification program (1967) there were many boars that were siring pigs that had in excess of five square inches of loineye muscle and less than 1.25 inches of backfat.  Rapid progress had been made in carcass traits.  Every issue of the breed magazines had page after page after page of data on certification.  Swine testing stations were running full capacity and performance testing in the swine industry was a serious matter.  There were 39 swine testing stations in 24 states (Henderson, C.R., 1975).


In 1975, Dr. C.R. Henderson of Cornell University published his paper on “Best Linear Unbiased Estimation and Prediction Under a Selection Model” in the journal of Biometrics.  Dr. Henderson, in his paper, developed a method to deal with data from animals that do not meet the requirements of random sampling.  The usual methods in place up to this point according to Dr. Henderson would yield biased estimates and predictions.  So after this work by Henderson, animal breeders were able to design data analysis methods that would increase the accuracy of the calculations.


It was not until January of 1981, that the American Yorkshire Club announced the beginning of its Sow Productivity Program.  This was the first such program in the industry that was available to all producers and that calculated breeding values.


American Yorkshire Club Sow Productivity Program


A Within Herd Selection Tool

In the early days of the development of the Yorkshire breed in America, much attention was paid to litter size and litter weights.  It was no more important then than it is today for purebred breeders and commercial men alike to make every effort to produce large litters of pigs from every sow he owns.  Efficiency of production is probably more dependent on number of pigs weaned per sow than any other single factor.


Recent research has shown sow performance traits to be heritable at about the 20% level, which means that progress can be made in these areas through selection.


What is Sow Productivity?

One definition of sow productivity is the ability of a sow to farrow large litters of live pigs and to give sufficient amounts of milk to make them grow rapidly until they are weaned.  In addition, the sows ability to perform this task on a regular basis is a factor to be considered.


How Can Sow Productivity be Measured?

There are basically two areas where measurement can be taken.

            1.  Prolificacy (Number of pigs produced)

            2.  Milking Ability (measured by the weight of the pigs nursed by the sow)



Prolificacy seems like a simple trait to measure.  However, it is important that prolificacy be measured by counting the number of pigs born alive.  Most swine producers will agree that number of pigs born alive is much more important economically than total number born.  For example, if a sow farrowed 14 pigs but only eight were born alive, it would probably have been better if she had farrowed only eight since they probably would have been larger and stronger.


There is one other important reason to select for pigs born alive, instead of total pigs born.  According to Irvin and Swiger (1984) of Ohio State University, the heritability of number farrowed alive is (.22 + .11) while the heritability of total number farrowed is (.18 + .10). On the other hand, the heritability of number born dead is higher than either (.35 + .12).  Therefore, if you select on the basis of total number born, and a good portion of these were dead at birth, you would theoretically make more progress in pigs born dead than in any other of the traits.



Milking ability in swine in not a real easy trait to accurately measure.  The only practical way is to measure the weight of the pigs that nurse the sow.  By doing this, we are assuming that sows which give large amounts of milk will wean pigs that weight more, thus giving us a good measure of her milking ability.


In order to accurately measure any trait, we must try to eliminate the environmental effects that would cause a difference in our measurement.  There are several environmental factors that affect the amount of milk given by a sow.  Some of these are as follows:


1.  Number of Pigs Nursed - Ideally we would have each sow nurse the exact same number of pigs.  Of course this is not possible, so we must first standardize the number of pigs nursing each sow as much as possible.  This is accomplished by moving pigs from large litters over to sows nursing smaller litters.  For example, if two sows farrow the same day and one has 12 and one has eight, you would move two pigs from the large litter over to the sow with the small litter to make both sows actually nurse ten pigs.  BE SURE TO EARNOTCH ALL PIGS BEFORE ANY TRANSFERS ARE MADE.


The transfer of pigs from one litter to another will not affect pedigree information for a sow. It is done only for the sow productivity record.  Number of pigs born and weaned for the pedigree will remain as is.  For example, a sow gets credit for all of her weaned pigs, even those nursed by another sow on the pedigree application.


Standardization of litters is much easier where several sows are farrowing fairly close to each other.  In smaller herds where there are only a few sows farrowing at the same time, it will be

more difficult.  The thing to remember is to try and even up the litters as much as possible and try to avoid any sow nursing less than six pigs or more than 12 pigs. 


Another reason for the standardization of the litter size is to do away with the environmental effect on gilts that are raised in large litters.  Revelle and Robison (1973) at North Carolina State University showed evidence that selection of gilts born and raised in large litters (12 or larger) will not lead to increased litter size in the next generation because of the environmental effect by being raised in large litters.


                2.  Number of Litters a Sow has Farrowed (Parity) - A gilt with her first litter will not perform the same as she will with her second and subsequent litters.  Therefore, some adjustments must be made to report all females on a sow-equivalent basis.


            3.  Season of the Year - Season of farrowing has a great effect on sow performance.  The conditions which exist in the farrowing house during different seasons can vary widely.  For this reason, in the sow productivity program, sows are compared only with their “contemporary group” or those sows which farrow during the same season.  A “season” may be a one week period, a month period, or longer.  All data from the program is based on a ratio of those sows that farrowed during one period or “season”.  The producer must decide what to include in one “contemporary group”.  The Yorkshire Club suggests that records be sent in on a monthly basis.  The important thing to remember is to group sows together that had an equal chance to perform.



The most important measurement that is taken in the sow productivity program is the weight of the litter at 21 days of age.  The age of 21 days (three weeks) has been selected because it should reflect milking ability more accurately than other times.  Pigs are too young to have eaten much creep feed and are old enough to have responded to the milk of the sow. 


It is recommended that all litters be weighed at exactly 21 days, but that may not be possible.  Breeders are allowed to weigh pigs from 14 to 28 days of age and then the weights are adjusted to a 21 day standard.  Here are the adjustment factors used to standardize the date weighed:







































Probably the most important thing a breeder must do in order to successfully have a sow productivity program is to have a convenient method of weighing the litters of pigs.  The total weight of the litter is taken so all of the pigs should be weighed together.  There are no doubt


many types of scales that could be devised to weigh the pigs and each breeder is responsible to develop his own system.  ACCURATE WEIGHTS ARE ESSENTIAL FOR THE PROGRAM.



Producers enrolled in the program are required to furnish data to the Yorkshire Association on forms furnished to them by the association.  The data includes the following:


1.         Sow name and registration number

2.         Sire of sow name and registration number

3.         Litter number

4.         Sow family name

5.         Parity of sow (number of litters she has farrowed)

6.         Number of pigs born in litter

7.         Number of live pigs in litter

8.         Number of pigs nursing the sow after transfer

9.         Number of pigs weighted at 21 days (14-28 days)

10.       Total litter weight at 21 days (14-28 days)

11.       Age of litter in days when weighed

12.       Farrowing date


The data for each breeder will be processed on the association’s IBM System 32 Computer as soon as possible after it is received.  The data output of the Sow Productivity Program is as follows:


1. Sow Productivity Report ranking all the sows in that particular contemporary group

    from highest to lowest by breeding value.  The specific information listed for each sow

    is as follows:


            a.  Sow name and registration number

            b.  Sire of sow and registration number

            c.  Litter number

            d.  Parity

            e.  Total pigs at birth

            f.   Live pigs at birth

            g.  Number at 21 days

            h.  Adjusted weight at 21 days

            i.   Breeding value

            j.  Farrowing interval


            2.  Summary averages for this farrowing group:


            a.  Number of litters included in this group

            b.  Average number born alive

            c.  Average number born total

            d.  Average number at 21 days

            e.  Average weight of litters at 21 days

            f.  Average farrowing interval

            g.  Litters per sow per year for this group


3. Sow ranking for entire herd.  This report puts the entire sow herd together and ranks

    them by breeding value from top to bottom.  This report includes the last group of

    sows submitted and also all the sows reported in the past.


            a.  Sow name and registration number

            b.  Number of records included for each sow

            c.  Sire of sow name and registration number

            d.  Last parity for each sow

            e.  Breeding value for each sow in herd


4. Sow ranking by family.  This report ranks all of the sow families in each herd

    according to breeding value.


            a.  Sire family name

            b.  Number of sows in family

            c.  Average breeding value for each sow family


5. Sire of sow ranking.  This report ranks all of the sires of sows according to the

                 performance of their daughters.


            a.  Name and registration number of sire of sows

            b.  Number of sows sired by each boar

            c.  Average breeding value for all sows sired by each boar



                The initial cost of the Yorkshire Sow Productivity Program was as follows:


            Initial enrollment fee - $25.00 per herd

            Cost per litter processed - $1.00 per litter


The American Yorkshire Club wishes to acknowledge the Ohio State University and especially Dr. Keith Irvin, Dr. L.A. Swiger, and Dr. Gene Isler for the development of the Ohio Sow Productivity Program and their help and cooperation in making the program available to the American Yorkshire Club.


The Yorkshire sow productivity program was an instant success.  After six months of the program over 60% of all Yorkshire litters recorded had sow productivity data included and for the first time a true performance pedigree was a reality.  Other breeds that were processed through the Yorkshire system were the Spots, Hampshires, Duroc and Landrace.



The STAGES program was developed in 1985 and announced by the American Yorkshire Club in January of 1986.  STAGES was developed by a team of scientists at Purdue University.  These included Dr. Dewey Harris, Dr. Alan Schinckel, Dr. Terry Stewart and Dr. Donna Lofgren.  Dr. Harris was located at Purdue but was USDA-ARS assigned.  The following was the initial announcement of the program.


The development of a Swine Testing and Genetic Evaluation System (STAGES) was initiated as a joint project between Purdue University, USDA Agricultural Research Service, USDA Extension Service, National Association of Swine Records (NASR), the Purebred Associations and the National Pork Producers Council (NPPC).  STAGES computer programs were implemented on national breed association computers to serve their members.


The development of STAGES involved several steps.  The six steps of development were:


STAGE 1: Within-herd genetic evaluation for post-weaning growth (average daily gain or days to 230 lbs.) and back thickness was developed for a single contemporary group.  A contemporary group is defined as all individuals having an equal opportunity to express their genetic potential. 

For example, a contemporary group might be a group of boars or gilts, within a month of age, tested on the same diet in the same facility.  Sires, dams, young boars and gilts off-test (5-6 months of age) will be evaluated simultaneously within each contemporary group.  Stage 1 is ready and the AYC can process those records NOW!  Stages 2 through 6 will be available approximately at six month intervals.  (Yorkshire Journal, January 1986).


STAGE 2: Genetic evaluation of post-weaning traits will be extended for multiple contemporary groups.  This procedure will bring forward information from past progeny of the sires and dams.  At this stage, sire evaluations will be adjusted for the predicted genetic differences of their mates.


STAGE 3: Revision of the current sow productivity program to include additional within-herd information from relatives to evaluate gilts, boars and their sires and dams.  Stage 3 will increase the accuracy of selection for the lowly heritable reproduction traits such as litter size and litter weight.


STAGE 4: Analysis of post-weaning traits (Stages 1 and 2) will be extended to include the options for individual or full-sib pen feed conversion and/or carcass data.  The options would allow inclusion of data from central test stations and intensive on-farm performance tests.


STAGE 5: The reproductive and post-weaning traits for multiple within-herd contemporary groups will be combined into comprehensive indexes.  Three alternative indexes will be calculated - a maternal, general and terminal sire index.  The maternal index will place greater emphasis on reproductive performance than the other indexes.  The terminal sire index will emphasize post-weaning performance.


STAGE 6: Across-herd sire evaluation for the reproduction and post-weaning traits will be developed.  When all six steps are completed, the program will analyze the records and evaluate all tested individuals within each breed including on-farm test, central test station and barrow tests.


Basic Concepts of STAGES

Several concepts are important to the discussion of selection procedures.  The first concept is that genetic variability exists within the swine population and is transmitted to progeny and descendants.  For seedstock herds to improve, genetically superior individuals must be selected.  However, it must be recognized that we do not know the true genetic merit of each individual, but instead must select based upon estimates of the animal’s genetic merit from available performance data.


The true genetic merit (breeding value) of the animal is the effect of all of its genes upon relevant traits.  The concept of breeding value is based on the fact that genes occur in pairs.  Selected individuals transmit a sample one-half of their genes or breeding value to each offspring.  For this reason, one-half of the breeding value is the expected progeny difference.  Genetic evaluation programs express the genetic merit estimates as predicted progeny deviations (PPD’s) as indicators of the animal’s breeding value or true genetic merit.


The predicted progeny deviation is an estimate based upon performance and sib or progeny data.  The PPD is equal to one-half the breeding value (PPD = ½ EBV) of either sires, dams or progeny.  Thus, PPD measures the effects of those genes an animal is expected to transmit to his/her offspring.  It is an estimate of how future progeny of the sire (or dam) are expected to perform relative to the average performance of the contemporary group, when mated to individuals of average performance and when the resulting progeny are treated alike.  The PPD for the mating of a specific male to a specific female is the sum of the PPDs for the two parents.


The important aspect in progeny deviations is to predict future progeny performance from the sample of performance records currently available.  Therefore, the predicted progeny deviations are regressed toward the average predicted progeny deviation, which is zero, depending on the number and distribution of performance, sib performance, and/or progeny performance records.  PPDs take into account the heritability of the particular trait (or the heritabilities and associations of the traits in an index).  The PPDs for feed consumption are estimated from performance information for growth rate and backfat which are genetically correlated with feed conversion.  The PPDs are reported in the same units of measure as the trait is recorded.  Deviations can be either a plus deviation or a minus deviation.


With each predicted progeny deviation, a possible change value (+ x) is presented in parentheses.  This possible change value is a measure of the accuracy (based on the number and distribution of available performance data for that individual and his/her close relatives) of the PPD in predicting future progeny performance.  The possible change measure indicates the amount of change, either plus or minus, that is possible in the predicted progeny deviation when additional progeny are included in the calculations.  The probability of change (in either direction) greater than the possible change measure is only one in three.  The chance of twice the possible change (in either direction) is only one in 20.


Because the PPDs are regressed toward the average depending on the number and distribution of records, PPDs are directly comparable, even though the numbers of records and the resulting possible change values are different.  This allows the seedstock producer to compare young performance tested sires and young replacement gilts with older sows.  These comparisons facilitate replacement decisions.


Contemporary Groups

The most accurate genetic evaluation is possible when individuals are compared to others in the same contemporary group.  Participants who collect performance information are the only ones who know how animals in their herds should be grouped.  ‘A contemporary group is a group of animals of the same breed or cross given similar treatment and equal opportunity to perform and express their true genetic potential.  Within a contemporary group, the animals should be treated as uniformly as possible including similar pen space and diet.  Contemporary groups should be of a short enough duration of time that the environment is as uniform as possible.  However, the contemporary groups should include enough animals to form a basis of comparison.  The participant must compromise between small, short-duration contemporary groups and larger, long duration contemporary groups.  The optimal strategy is to include as many animals as can be fairly compared.  For example, a contemporary group might be those sows farrowing within a one month period in the same facility, or a group of young boars within one month of age raised together.


Different genetic groups should be treated as different contemporary groups.  For example, if some females are mated purebred and others are mated to produce F1 progeny, they must be submitted as two different contemporary groups.  The program also allows participants to identify sub-contemporary groups.  The sub-contemporary group option is to be used when animals of similar age have been subdivided into different facilities, fed different diets or managed differently.  Examples might include: sows farrowing together but fed different lactation diets, or boars within one month of age fed different diets or tested in different facilities.  Even though the animals were evaluated at the same time, the environments are different and animals should be divided into two sub-contemporary groups.


Selection Objectives

To meet the genetic needs of their commercial-producer customers, purebred breeders should select for a balanced combination of economically important traits.  The best and most easily understood post-weaning index is one which evaluates relative profit potential ($/hog) as the estimated market value minus post-weaning labor, facility and feed costs.


The market value of each hog is based on the NPPC pork Value Program.  For each one-tenth inch reduction in backfat thickness, market value increases by 1.05 percent.  Taken from NPPC tables, an animal with over one inch of backfat ha a value less than 100%.  In the recommended

post-weaning index, market value of the progeny is calculated as the product of market weight (230 lbs.) Base price ($45.00) and the animal PPD or NPPC pork value relative to a 97.4% base (1.25 inches of backfat).


Labor and facility costs are estimated from the expected days from weaning to market and daily labor and facility costs.  The growth rate of each animal’s progeny is used to predict the days from weaning to market.  The recommended index uses a labor and facilities cost of $.17 per pig per day.  Although feed consumption data are not included in Stage 1, feed consumption PPDs are predicted from the relationship between growth rate and backfat.  Each animal’s progeny feed costs are estimated by the product of its expected progeny feed conversion (relative to a 3.5 lb. feed per lb. of gain base) live weight gain (215 lbs.) And feed cost ($.07/lb. or $140/ton).


The indexes are in units of dollars per progeny produced.  The recommended index is the value of each animal per progeny produced using average production costs.  For example, if a boar has an index of $2.00 per oz., the value per offspring marketed should average $2.00 more than the offspring from a boar having an index of 100.


STAGES allows each seedstock producer to modify the indexes by introducing different economic values.  The seedstock producer can change the emphasis the index places on backfat thickness by changing the NPPC marketing value percentage.  The NPPC marketing value percentage is the percentage of hogs sold to packers with updated carcass value purchase programs similar to the NPPC Pork Value Program.  The recommended base index assumes that 100% of the hogs are sold to a packer with updated carcass value purchase programs.  This emphasis on leanness will select the hogs with the least cost pre pound of lean pork produced.  This is the overall efficiency goal for the pork industry.


It has been estimated that 40% of the U.S. hogs currently are being slaughtered at plants with updated pork-value pricing systems.  This percentage will likely increase and approach 100 percent in the future.  To select seedstock for the future, a 100 percent value is preferred.  The minimum emphasis a seedstock producer should place on backfat is 40% NPPC marketing as already 40% of the hogs are being slaughtered at plants with pork-value pricing systems available.  The calculations assume that non-NPPC marketing places only one-third the emphasis on leanness relative to marketing.


The relative emphasis the index places on growth rate is dependant on the daily labor and facility cost.  The base value which includes all daily non-feed costs is used in the recommended index.  Seedstock producers with commercial customers operating high investment growing-finishing facilities should consider using a higher daily labor and facility cost.  Likewise, seedstock producers with commercial customers operating low investment facilities might use a lower labor and facility cost.


The feed cost per pound should be considered as the future average feed cost (delivered to pigs), including mixing and handling for a 15 percent crude protein growing-finishing diet.  Herds in the southeast will generally have higher feed costs than producers in the Midwest.  Thus, some breeders might prefer an index with a feed price deviating from the base value for the recommended index. 


If the recommended index is acceptable to the owner as a basis for ranking his animals, the blanks for the owner’s optional index coefficients may be left blank.  If the owner’s optional index coefficients are left blank, the recommended index coefficients are used in calculating the owner index.  In this case, the owner index and recommended index are identical.  (Yorkshire Journal, January 1986)


Evolution of Genetic Evaluation

The genetic evaluation systems employed by the Yorkshire Club have not remained static, but have been dynamic since the first genetic evaluation was implemented by that organization in the 1980s. Since that time other pure breeds have implemented various forms of genetic evaluation using the latest computer and software technologies. Dr. John Mabry of the University of Georgia and his graduate students played instrumental roles in developing the Purebred Across-herd Genetic Evaluation (PAGE1) systems for the Duroc and Hampshire breeds and refining those that had already existed. Their tireless efforts have helped form a cooperative effort among the University of Georgia and Purdue University researchers to help make the genetic evaluation program used by the pure breeding organizations a preeminent system that is recognized worldwide.


Under the direction of Darrell Anderson, CEO of the National Swine Registry, the Yorkshire, Landrace, Duroc, and Hampshire breeds formed a single genetic advisory committee formed in 1994. The advisory committee continues to be made up of leading swine geneticists from several land-grant universities. The original members of the committee included Dr. John Mabry, University of Georgia, Dr. Tom Baas, Iowa State University, Dr. Allan Schinckel, Purdue University, Dr. Todd See, North Carolina State University, and Dr. Ron Bates, Michigan State University. Dr. Maynard Hogberg of Michigan State University has served as an ex-officio member and Dean Compart has served as the producer representative since the inception of the committee. Dr. Tom Long, University of Nebraska served on the committee for a short time before he moved to private industry. Dr. Ken Stalder, University of Tennessee, replaced Dr. Long on the committee in 2000. The committee has and continues to provide the organization with direction concerning its genetic programs and the systems used to predict the genetic merit of breeding animals. Dr. Allan Schinckel of this committee developed curvi-linear adjustments for backfat and loin muscle area and equations for the prediction of pounds of lean for each animal. The adjustments were adopted by the genetic advisory council and provide a more accurate method of adjusting backfat and loin muscle values. The advancement provides less credit for animals that are ultra lean and heavy muscled and improves the accuracy of the genetic merit that is predicted for each registered animal. There are numerous other examples of the ideas and technical tools that have originated from the work of the genetic advisory committee.   


Today the program used by the purebred associations is run in house rather than contracting the work to one of the cooperating universities. Additionally, the system utilizes a moving genetic base and calculates breeding value estimates daily. The programs used to evaluate the genetic merit of animals continue to be dynamic.  Several of the previously mentioned advancements continue to aid seedstock producers in accurately identify animals with superior genetic merit.


Many of the advancements made in the procedures to evaluate the genetic merit of animals have originated with the organization sponsoring today’s conference, the National Swine Improvement Association otherwise known as NSIF. Since its inception in 1975, the National Swine Improvement Federation has provided the swine industry with testing procedures used on-farm and in testing stations, various indices used to predict genetic merit of animals, economic weights, adjustment factors, ultrasonic certification programs and other items used on a regular basis by those producing breeding stock for the swine industry. The Federation is made up of industry, academia, purebred breeders, and genetic companies. Its board of directors and members of various committees all are derived from its membership. The National Swine Improvement Federation continues to provide its membership and the swine industry in general with educational material like the Genetic Fact Sheets and guidelines for evaluation of swine like the design of contemporary groups. These examples show the importance and outstanding contributions that the National Swine Improvement Federation has made during the first 25 years. With continued leadership from its membership, many more advances and improvements can be expected from the Federation. The improvements initiated will benefit the swine industry worldwide.



Swine performance testing in the United Stated was started in 1938 by the National Association of Swine Records, which is an organization made up of breed secretaries.  The first performance program was the production registry (P.R.) program which tested the ability of sows to farrow and raise pigs to 56 days of age.  The next significant program was the litter certification program which included P.R. data as well as carcass measurements.  In the early 1950's, swine test stations became a reality and many boars as well as slaughter barrows and gilts were tested in central facilities.


The work of Dr. C.R. Henderson of Cornell in 1975 made it possible to accurately evaluate populations of swine that were not randomly selected.  As a result, the modern-day programs became possible where computers could deal with large data sets and provide more accurate results than was previously possible.


Keith Irvin and coworkers at Ohio State University developed the sow productivity program that was initiated in 1981 by the American Yorkshire Club.  It became a very popular program not only for Yorkshires, but for other breeds as well. The more advanced STAGES program was developed at Purdue University by Drs. Dewey Harris, Donna Lofgren, Allan Schinckel, and Terry Stewart in 1985, and was initiated by the Yorkshire Association in January of 1986.  In the 1990s, the Landrace breed also implemented the STAGES program while the Duroc and Hampshire breeds implemented the PAGE1 system developed by Dr. John Mabry and co-workers at the University of Georgia. STAGES has been fine-tuned to become the present-day ultimate program using the science that is presently known to calculate highly accurate estimates of genetic worth.




Hazel, L.N. and E.A. Kline. 1952. Mechanical Measurement of Fatness and Carcass Value on

Live Hogs. J. Anim. Sci. 11: 313-318.


Henderson, C.R. 1975. Best Linear Unbiased Estimation and Prediction under a Selection

Model. Biometrics. 31: 423-447.


Irvin, K.M. and L.A. Swinger. 1984. Genetic and Phenotypic Parameters for Sow Productivity.

J. Anim. Sci. 58:1144.


Revell and Robison. 1973. An Explanation for the Low Heritability of Litter Size in Swine.

J. Anim. Sci. 37:668


2000 NSIF Proceedings