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Genetic Parameter Estimates for Reproductive Traits of Male and Female Littermate Swine¹

Oklahoma Agricultural Experiment Station, Stillwater 74078

Abstract

Reproductive traits of purebred and crossbred pigs produced in a four-breed diallel mating system using the Duroc, Landrace, Spotted and Yorkshire breeds were collected for five consecutive farrowing seasons (two farrowing seasons/year) beginning in fall 1976. Paternal half-sib heritabilities and genetic correlations for testicular traits (120 boars from 36 sires), serum testosterone (TE) and luteinizing hormone (LH) concentrations before and after treatment with gonadotropin releasing hormone (GnRH; 131 boars from 37 sires) and breeding performance traits (151 boars from 38 sires) were estimated. Heritability estimates were generally small to moderate except for sperm/gram testis (SGT), LH concentrations before (LHO) and at 3 h (LH3) after treatment with GnRH (.73 ± .48, .61 ± .46 and 1.19 ± .45, respectively). A large positive genetic correlation was found for LHO with LH3 (.94 ± .39), while a negative relationship existed for LH3 with TE concentrations at 3 h after GnRH injection. The genetic correlation between a boar's average first service conception rate and average conception rate also was significant (.82 ± .54). Genetic correlations among littermate traits would suggest that selection for decreased age at puberty in gilts could cause an increase in LH concentrations in boar offspring, before and after GnRH injection, and may also have adverse effects on their ability to settle females. Selection for increased weight at puberty of gilts could cause TE concentrations of boar offspring to increase while having little effect on their breeding performance.

¹ Published Paper No. 4902 Journal Series, Oklahoma Agr. Exp. Sta., Stillwater and a contribution to Regional Project NC-103, Genetic Improvement of Efficiency in the Production of Quality Pork.

² Present address: Anim. Sci. Dept., Univ. of Missouri, Columbia 65211.

³ Anim. Sci. Dept., Oklahoma State Univ., Stillwater 74078.

⁴ Present address: Anim. Sci. Dept., Univ. of Nebraska, Lincoln 68583.

⁵ Present address: Agr. Dept., Northeastern Oklahome A&M College, Miami 74354.