On-farm testing programs are designed to assist seedstock producers
in evaluating their animals in a systematic manner. The programs
described in this chapter will assist breeders in: 1) selecting
of boars and gilts for use in their breeding programs; 2) providing
procedures for identifying superior individuals within strains,
lines, or breeds; 3) supplying high quality performance tested
seedstock; and 4) communicating unified terminology and breeding
stock selection guidelines to the pork industry.
The objectives of on-farm testing programs are best achieved through
whole herd testing. Testing only a selected sample of the herd
yields limited and biased information. Expected Progeny Differences
(EPD) that describe the genetic merit of each animal as a parent
can be estimated most accurately by combining all of the available
information on a pig and its relatives.
Accuracy is an extremely important part of any testing program.
Since most producers have the ability to adequately conduct performance
tests, professional assistance from breed associations, testing
organizations, state Cooperative Extension Services, and private
commercial concerns is available to aid producers in the mechanics,
record processing, and reporting of data from a testing program.
Further, the involvement of agents without a vested interest
in the results may provide greater assurance of accuracy and serve
as motivation for the producer to collect and use the appropriate
Pigs should be evaluated within contemporary test groups.
A contemporary group is a group of pigs of the same breed or
breed-cross, born in a short period of time (no more than six
weeks), fed the same diet (see Appendix A for sample diets), and
raised in the same facilities under the same management. These
test groups should be managed uniformly, and all pigs within the
test group should be given an equal opportunity to perform. Contemporary
groups should consist of at least 20 pigs from at least five litters
and at least two sires. Testing smaller groups will lead to inadequate
comparisons and less reliable EPDs.
Breeders who choose to use either within-herd EPD or across-herd
EPD programs should follow the recommendation that all
pigs be tested. Otherwise, breeders should use a base program
rather than the within-herd EPD or across-herd EPD programs.
Selection of animals to be tested will lead to misleading and
incorrect information on the EPDs being calculated. Each record
should be expressed relative to the test group or herd average
by the use of deviations from the average, or EPDs.
Seedstock on-farm testing programs should encompass whole herd
testing of sow productivity and all performance traits (on all
intact males and all females). In reporting data, deviations
from the average within contemporary groups should be used. Seedstock
programs should also include sire and dam litter summaries. When
ranking animals, selection indexes (see p. 14) should be used
to assign appropriate emphasis to each of the various traits.
Participants of the base swine improvement program should
meet the following minimum recommendations.
An individual breeder may wean at any time, but litter weight should be recorded before weaning and as near to 21 days of age as possible for the most accurate assessment of sow milking ability. NSIF recommends weighing pigs between 14 and 28 days and adjusting to a 21-day basis. Post-farrowing litter weights may be adjusted to a 21-day basis by using the following multiplicative factors:
The following equation was used to compute the tabular values and can be used to directly adjust litter weight to a 21-day basis:
Producers using a protocol that involves weaning pigs at an extremely
young age (e.g., Segregated Early Weaning) should state how sows
are evaluated for productivity. NSIF recommends pigs be weaned
no earlier than 10 days of age; using factors in Table 2 will
permit sows to be ranked on the Sow Productivity Index (see page
14). The closer to 21 days of age pigs are weaned, the more accurate
the adjustment will be. If pigs must be weaned earlier than 10
days of age, use an alternative index (page 14).
If possible, litters should be standardized to between 8 and 12 pigs per litter within 24, but not later than 48, hours after birth. Pigs selected for transfer should be average in size. Males, rather than females, should be transferred if possible. After standardization, the number of pigs reared in the litter should be recorded B all pigs given to the sow to raise, including foster pigs. Standardization of the post-farrowing weight record will prevent discrimination against a good milking sow or gilt that has a lesser opportunity because of smaller than optimum litter size. The litter weight (already adjusted to a 21-day basis) should be standardized to 10 pigs by adding the appropriate value from the following table:
Post-farrowing litter weights should also be adjusted to a mature sow equivalent by adding the following numbers to the record based on the parity of the female:
The adjustment factors in Tables 1-4 were derived for general purpose use from large data sets. NSIF recommends that whenever possible, specific adjustment factors be derived from data sets for specific populations, for use in those populations specifically.
If an endpoint weight different from 250 lb is used, refer to Equations 1A and 1B in Chapter 4 to calculate PPL.
Calculation of EPDs on all pigs in a herd using all available information is a requirement for these programs. In addition to data on the individual, information should include full-sib, half-sib, parental, and progeny data updated regularly. Computer programs are commercially available for the calculation of within-herd EPDs. Procedures, models and genetic parameters used in within-herd genetic evaluations should be well documented, and preferably be those recommended by NSIF.
Across-herd breeding value estimation should use multiple trait animal model procedures and genetic parameters derived from the data. An accuracy value that reflects the amount of information used in the genetic evaluation should also be made available. Purebred breeders can participate in across-herd genetic evaluation programs through the National Association of Swine Records (NASR). Procedures, models and genetic parameters used in across-herd genetic evaluations should be well documented and preferably be those recommended by NSIF.
To make accurate selection decisions, commercial producers who select replacement animals from their own herd should measure the performance level of their animals. Obtainable goals should reflect the changes in performance that the producer considers necessary to develop and maintain a profitable program. The records that commercial producers should keep and the traits chosen for genetic improvement are dependent on the economic value of the traits and the extent to which producers plan to utilize the records in decision making. These essential records should provide the basis for a diagnosis of the program's weaknesses as related to the producer's goals, and serve as an early warning tool to monitor potential program problems. Because each producer's goals may differ, and producers' physical operations vary, the traits chosen and level of performance desired may not be the same for all producers. At a minimum, however, all commercial producers should utilize records on sow productivity and boar performance to evaluate and monitor herd production. The Pork Industry Handbook Factsheet 100 has additional information on types of records and their use.
For commercial farms, maximum hybrid vigor is essential in the female. Therefore, planning and implementing a crossbreeding program and keeping a record of female breed composition are important. A sow productivity program should aid in selecting replacement gilts from the most productive sows in the herd and serve as a basis for culling the least productive females. To achieve high production standards, sows need to be prolific, have good milking ability, and rebreed within 7 days post-weaning. Sows that fail to settle in two estrous cycles following weaning should be culled. Computer programs and sow record cards can help as systematic tools to record production activities and performance records. For producers who select replacement females from within their own herds, performance information on individual gilts and their dams is important, and use of a selection index is recommended. The accurate selection of replacement gilts can be accomplished by following the base on-farm program.
Boars purchased from seedstock producers should come from the top 50% of their test group in test station and on-farm programs. Whenever data are available, commercial producers are strongly encouraged to use EPDs when purchasing animals or semen. Boars selected for use in an A.I. program should meet higher standards and be in the top 10 percent of the population evaluated.
Environmental influences make it difficult to compare pigs tested at different locations, at different times, or under different management. Using selection indexes based on contemporary group comparisons will allow comparisons of animals in the same test group. Keep in mind, indexes are not appropriate for comparing different groups of animals.
The traits used in the calculation of NSIF selection indexes are defined as follows:
These indexes will average 100 for each test group and should have a standard deviation of about 25. A test group should have approximately the following distribution of index values:
If EPDs are reported, animals may be evaluated with similar indexes. The simplest index consists of all the EPDs added together. For example, if a producer is interested in litter size, growth and backfat, the index would be:
Use of economic values for each trait will weight the genetic information for the relative economic importance of each trait. Using the economic values in Table 8 (Appendix E) for the same traits would give this index:
For more information on indexes, see Appendix E.
The following items are herd health recommendations for on-farm testing programs for seedstock producers.
Effective merchandising depends on the integrity of the breeder, coupled with the use of accurate, complete performance information explained by well-defined terms relating to the product to be sold. The use of misleading statements that may be deceptive, impossible claims, or use of selected portions of the total record in the merchandising of performance-tested swine is strongly discouraged. Every possible effort should be made to inform and educate swine producers on the use and interpretation of performance records.
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