NPPC Maternal Sow Line Genetic Evaluation Program

Rodney Goodwin, Ph.D.

The National Pork Producers Council (NPPC) Genetic Programs Committee has developed these guidelines for a National Genetic Evaluation Program that will evaluate maternal sow lines for reproductive growth, carcass, and meat quality traits. This program began in January 1997. It will in 1999, with results available in 2000.


American Diamond Genetics ` F1 female

Danbred USA F1 female

DeKalb Swine Breeders Maternal Line female

DeKalb Swine Breeders NE Index *DeKalb F1 female

Newsham Hybrids USA Maternal Line female

American Yorkshire Club-American Landrace Assn. F1 female


1. Measure lifetime sow productivity, defined here as through four parities.

2. Evaluate the 50% of market pig performance due to maternal line genetics.

Terminal crossbreeding systems require production of specialized sire and dam lines. The annual replacement rate of maternal line females varies from 40%-80%. Higher replacement rates decrease the proportion of more productive higher parity females in the herd. High replacement rates increase the cost of breeding stock per pig and highlight the importance of sow longevity.

The proposed program will evaluate sow reproduction efficiency through four parities. Reproductive traits include:

n weight of pigs weaned per day of sow life

n litter size

n litter weight

n re-breeding interval

n salvage value

n feed usage

Progeny will be evaluated for growth, carcass, and meat quality traits using methods similar to the NPPC Terminal Sire Line National Genetic Evaluation Program (NGEP).

The program will end when the last sow from the third gilt intake group weans her four litter.


Due to the size of the program and unbiased culling of females, several additional production research questions concerning individual sow management will be addressed. Many producers found the "spinoff" projects in SEW, AI, and meat quality to be valuable additions to the Terminal Line Program.


Genetic type of females for entry

A genetic population has litters where 90% of the sires and 90% of the dams were born in the population during the last five years. The parnet lines of a Maternal Line meet the standards of a genetic population. Entries to this program are American Diamond Genetics, Danbred, DeKalb Maternal Line, DeKalb-NE Index Line, Newsham Hybrids and Yorkshire-Landrace F1 females.

Genetic types of boars for maternal line program

Danbred boars were selected to produce 100% heterosis in the test progeny. All parity groups of sows will be serviced by artificial insemination as directed by the Genetic Programs Committee. All vasectomized boars used for estrus detection in the program were entered with female lines through SEW stations.

Source herd health status

All herds of origin of program gilts and boars meet health standards for interstate movement. No protocols for treating pigs prior to entry in SEW stations were used.

Segregated early weaning (SEW) program

Gilts and boars were entered in an SEW station at 8-15 days of age. New 1,000 pig wean-finish buildings were contracted for SEW stations. Procedures and medication products used were approved by the Genetic Programs Committee.

Female culling procedures for the program

1. Death

2. If a female of any age is declared unfit due to injury or illness by the attending veterinarian and herd manager.

3. If a gilt fails to conceive during a sixty (60) day breeding period. Gilts will begin breeding season not earlier than 210 days of age.

4. If a gilt fails to express estrus by 300 days of age.

5. If a sow fails to conceive after 50 days post weaning.

6. 21 days after farrowing fourth litter.

Measure of sow performance, all parities

1. Pigs per day of life. Total pigs ¸ age at culling.

2. Pounds of pigs per day of life. Total pounds of pigs (21 day litter wts) ¸ age at culling.

3. Number of pigs born per litter.

4. Number of pigs born alive per litter.

5. Birth weight of litters - born alive.

6. 10 day litter weight if processing and castrating.

7. 21 day litter weight.

8. Number of pigs weaned at 21 days.

9. Sow weight change (sow weight at farrowing - sow weight at weaning)

10. Sow feed intake during lactation.

11. Hours to estrus after weaning.

12. Total feed intake.

13. Salvage value-weight at culling.

14. Nonproductive sow days.

Measures of longevity

1. Sow age at culling in days.

2. Body condition score based upon backfat depth.

Measures of growth

1. Days to 250 lbs (test females and progeny)

2. Daily gain on test, progeny

3. Feed efficiency, progeny

4. Daily feed consumption, progeny

5. Leg soundness score, progeny.

Measures of carcass merit* (progeny)

1. Dressing percentage.

2. Off midline backfat thickness at the tenth rib.

3. Midline backfat thickness at the last rib.

4. Midline backfat thickness at the last lumbar vertebrae.

5. Loin muscle area at the tenth rib.

6. Carcass length.

* Traits measured according to NPPC publication, Procedures to Evaluate Market Hogs.

Measures of loin muscle meat quality (progeny)

1. Minolta Chromameter reflectance and Hunter scale color.

2. Ultimate pH of loin.

3. Total loin lipid content.

4. Loin muscle color score.

5. Loin muscle marbling score.

6. Loin muscle firmness score.

7. Water holding capacity and drip loss of loin muscle.

All progeny test pigs will be classified by halothane genotype using the DNA probe method.


The size of the program is based upon the number of records needed per Maternal Line entered. Longevity measures are used to size the program. A statistical difference of .5 pigs per litter should be detected at 95% probability level.

Dr. O.W. Robison has calculated the number of records based upon each sire of test females being represented by three litters with three test females per litter. Each test female that reaches the breeding herd (210 days of age) is a record for longevity. It is estimated that 90% of gilts delivered to SEW station will reach the breeding herd. A heritability of .15 is assumed for longevity traits. Assurance rate is 75% and significance rate is 5%.

The six Maternal Lines entered in the evaluation program provided 3,258 females (92%) that will have longevity records (3,549 females entered to SEW nurseries).


Loss Rate

100 Gilts


SEW death loss rate




Gilt development death & injury loss rate


90 (longevity record)


Gilt reproductive failure rate


63 farrow P1

P1 re-breeding loss rate


50 farrow P2

P2 re-breeding loss rate


42 farrow P3

P3 re-breeding loss rate


35 farrow P4

There should be 190 litter records for each original 100 gilts entered in the SEW station.


All gilts and vasectomized boars entered in the Maternal Line Program were sent to an SEW station. Wean-finish facilities were used to grow these pigs. Three intakes of gilts (Feb., March, April, 1997) were done. No pig was older than 15 days of age at entry. Health protocols were approved by attending veterinarians. Program protocol was:

1. Naxcell injected on days 1, 2, and 3 of entry.

2. Ivomec at entry.

3. Water medication for first 3-7 days per veterinary recommendation.

4. Individual ear tag applied.

5. Penned by genetic type and weight.

6. Vaccination for PRRS at 4-5 weeks of age.

7. Two vaccinations for mycoplasma pneumonia.

8. Vaccination for Swine Influenza.

Leg soundness, and weight were recorded at the end of gilt development. All-in all-out management procedures were followed at each wean-finish unit. Gilts were culled from the program for illness of injury by recommendation of the attending veterinarian and herd manager.

At approximately 150-180 days of age, gilts and boars were taken to the two sow units. Gilts were transported, mixed, and exposed to boars to stimulate estrus. Breeding began after gilts were 210 days of age. All gilts are mated at second or later estrus. Gilts are mated to fill two contracted breeding gestation-lactation 1600 sow production units. A sixty day breeding period will be observed for gilts that are held open due to farrowing space requirements. Gilts were vaccinated for leptospirosis, parvovirus, and erysipelas when moved to sow units. Gilts were given an electronic ID eartag at entry to the breeding unit.


Gilts will be mated after 210 days of age at their second or later estrus. If excess females are in heat during a week, the breeding manager will try to get females with most estrus periods mated. Females intentionally not mated due to lack of farrowing space will be given another estrus period before culling. Each gilt will receive at least two doses of semen per mating period. Gilts will be pregnancy checked within 60 days post service.


All females will be weighed and backfat thickness measured when moved to a farrowing crate. Females will also be weighed and backfat thickness measured at weaning. Litters will be equalized by crossfostering.

All females will be fed ad lib from weaning until mated. After being mated, all females will be limit fed for 14 days to enhance embryo survival.

The gestation feeding level for each female will be determined by considering current sow weight, lactation weight loss, desired sow weight at next farrowing and backfat thickness. This approach is designed to optimize each sow's chance for success. Recommendations of seedstock suppliers regarding desired parameters is welcome.


A barrow or a gilt from each litter (1 progeny/female entered) will be sent to a wean-grow station at 10-21 days of age. After completing the SEW program, these pigs will be transferred to a test facility for growth trait evaluation. As pigs reach 250 lbs, they will be sent to a packing plant for carcass trait evaluation. A loin muscle sample from each pig will be evaluated for meat quality. All test pigs will be classified by halothane genotype using the DNA probe method.

Progeny pigs not being tested will be sold as early weaned feeder pigs (17-24 days of age) to generate cash flow.