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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Publications at this Location » Publication #420727
Research Project: Discovery of Novel Traits to Improve Efficiency and Sustainability of Different Sheep Production Systems

Location: Livestock Bio-Systems

Title: Estimates of genetic parameters for growth, reproduction, wool, and carcass traits in the U.S. Polypay sheep

Author
item SALEEM, ALI - Purdue University
item ROCHA, ARTUR - Purdue University
item YAZAR GUNES, HILAL - University Of Nebraska
item Murphy Jr, Thomas
item LEWIS, RON - University Of Nebraska
item BRITO, LUIZ - Purdue University

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: 4/3/2025
Publication Date: 1/15/2025
Citation: Saleem, A.H., Rocha, A.O., Yazar Gunes, H., Murphy, T.W., Lewis, R.M., Brito, L.F. 2025. Estimates of genetic parameters for growth, reproduction, wool, and carcass traits in the U.S. Polypay sheep [abstract]. In proceedings: Plant and Animal Genome Conference. January 10-15, 2025, San Diego, CA. P237.

Interpretive Summary:

Technical Abstract: The Polypay is a sheep breed developed in the U.S. and is known for maternal traits like fertility, prolificacy, non-seasonal breeding, and milk production. Sheep breeders aim to genetically improve these economically important traits, which require up-to-date and accurate estimates of genetic parameters. However, the parameters used in the National Sheep Improvement Program (NSIP) were last estimated many decades ago. Therefore, we used the BLUPF90+ software with the AI-REML algorithm to re-estimate genetic parameters for growth, reproduction, wool, and carcass traits in Polypay animals using data collected from 1980 to 2023. The pedigree consisted of 127,693 individuals. Animals with phenotypic records were the progeny of 2,451 sires and 23,163 dams. Data provided by NSIP included lamb body weight at birth (BWT; n =106,909), weaning (WWT; n = 69,811), early post-weaning (PWTE; n = 51,119) and late post-weaning (PWTL; n=10,365), and post-weaning ultrasound 12th rib backfat depth (PCfat; n=1,170) and eye muscle depth (PEMD; n=1,168). Reproductive traits included the number of lambs born (NLB; n=55,994) and weaned (NLW; n=55,994) and post-weaning scrotal circumference (PSC; n=1,081). Additionally, yearling greasy fleece weight (YGFW; n=2,301) and post-weaning fecal egg count (PFEC; n=3,160) were available. Phenotypes were pre-adjusted for birth-rearing type, dam’s age, and age at measurement, and analyzed using a univariate animal model. Contemporary group—a concatenation of flock, year, season, management group, sex, and, excluding BWT, recording date—was the only fixed effect fitted in the model. For the body weight traits, direct and maternal additive, without their additive covariance, and maternal permanent environment were fitted as random effects. For ultrasound traits and PFEC, only a direct additive random effect was included, with maternal permanent environment added for YGFW. Since NLB and NLW were measured repeatedly, the model fitted included direct additive and animal permanent environmental random effects. A random residual was included in all models. Body weight traits were estimated to be low to moderately heritable [0.09 (0.01) – 0.27 (0.03); WWT – PWTL] with minor to moderate influence from maternal additive genetic [0.15 (0.01) – 1.73 (0.29); BWT – PWTE] and maternal permanent environmental [0.13 (0.01) – 4.33 (0.29); BWT – PWTE] effects. Ultrasound traits were found to be low to highly heritable [0.09 (0.05) – 0.68 (0.07); PCfat – PEMD]. For reproductive traits, heritability estimates ranged from low to high [0.03 (0.004) – 0.48 (0.10); NLW – PSC]. Both YGFW and PFEC were moderately heritable [0.34 (0.05) and 0.36 (0.05), respectively]. Repeatability estimates for NLB and NLW were low [0.15 (0.01) and 0.07 (0.004), respectively]. Some of these estimates were consistent (WWT) with previous NSIP evaluations while others were slightly lower (PWTE, PCfat, NLB, NLW, YGFW) or slightly higher (BWT, PWTL, PEMD, PSC, PFEC). These updated estimates indicate that all the traits evaluated are under genetic control and can be improved through genetic selection. Future work will incorporate genomic data and calculate genetic correlations among traits for enhanced selection strategies in the U.S. Polypay sheep.