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Genotypic and Phenotypic Parameters of Milk Production in Primiparous Duroc Sows¹

North Carolina State University, Raleigh 27695-7621

Abstract

Weigh-suckle-weigh procedures were used to estimate milk production of 259 primiparous Duroc sows. Litter size was standardized to six pigs at 1 d of age in 48 of the litters. Three measurements were obtained, with 2-h intervals between sucklings, at approximately 21 d postpartum. The sum of milk obtained during periods two and three (milk23) appeared to be a more accurate reflection of milk production than individual measurements. Heritability estimates for milk23 in unstandardized litters from daughter-dam regression (95 pairs) and paternal half-sib correlations (88 sires) were .27 ± .15 and .20 ± .56, respectively. Heritability estimated from paternal half-sibs for 21-d litter weight in unstandardized litters was .70 ± .57. Daughter-dam regressions yielded heritabilities for 21-d litter weight of -.05 ± .18 in unstandardized litters and .35 ± .36 in standardized litters (16 pairs). Correlations among milk production, 21- and 35-d litter weight, survival and litter size were similar in unstandardized and standardized litters. Correlations between milk production and 21-d litter weight ranged from .45 to .64. Correlations between milk production and survival were approximately .35. Litter size at 21 d accounted for 10 to 28% and 72 to 80% of the variation in milk production and 21-d litter weight, respectively. Milk production accounted for 20 to 41% of the variation in 21-d litter weight and for 8 to 19% of the variation in survival. Results of this study indicate that after a minimal amount of milk is present, milk yield has a relatively small influence on 21-d litter weight and survival. Even when litter size was standardized at 1 d, the number of pigs at 21 d was the most important factor in 21-d litter weight.

¹ Paper No. 9678 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh.

² Current address: c/o Anim. Sci. Dept., Univ. of Nevada, Reno 89557-0097.

³ Dept. of Anim. Sci., North Carolina State Univ., Raleigh 27695-7621.