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Selection for Ovulation Rate in Swine: Correlated Response in Carcass Traits¹

University of Nebraska, Lincoln 68583^{3 ,4,}

Abstract

Carcass data were collected for four traits on 179 Select and 187 Control line barrows in generations 3 through 8 to evaluate correlated responses to selection for increased ovulation rate in swine. Traits involved were carcass length, carcass backfat thickness, loin eye area and percent ham and loin. Two barrows were randomly selected for slaughter from each sire group with the restriction that barrows selected from a sire be from different litters (half-sibs).

Paternal half-sib estimates of heritability obtained were 1.12 ± .29, .94 ± .30, .76 ± .30 and .52 ± .31 for length, backfat, loin eye area and percent ham and loin, respectively. Estimates of genetic and phenotypic correlation among the traits were length with backfat –.48, –.38; length with loin eye area .00, –.05; length with percent ham and loin .47, .22; backfat with loin eye area –.73, –.23; backfat with percent ham and loin –.76, –.34; and loin eye area with percent ham and loin .58, .27.

Selection for ovulation rate was effective, resulting in a realized heritability of .40 ± .06 based on the regression of response on cumulative selection differential. Regressions of line difference on generation number for the four carcass traits were nonsignificant. Estimates obtained were .10 ± .07 cm for length, .06 ± .03 cm for backfat, –.28 ± .27 cm2 for loin eye area and –.21 ± .13 for percent ham and loin. Estimates of realized genetic correlation obtained between ovulation rate and length, backfat, loin eye area and percent ham and loin were –.16, .52, –.23 and –.52, respectively. Selection for ovulation rate did not result in statistically significant correlated response in any carcass traits, although there was a slight tendency for a reduction in overall carcass merit over time.

¹ Published with the approval of the Director as Paper No. 5238, Journal Series, Nebraska Agr. Exp. Sta. Research reported was conducted under Project 13-1.

² Present address: University of Nebraska, North Platte Station, North Platte.

³ Department of Animal Science.

⁴ This research was supported in part by a cooperative agreement with the Agricultural Research Service, USDA.