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Selection for Evaluation Rate in Swine: Correlated Response in Age and Weight at Puberty, Daily Gain and Probe Backfat¹

University of Nebraska, Lincoln 68583³, ^,4

Abstract

Seven generations of direct selection for ovulation rate were evaluated to determine the magnitude of the correlated response in age and weight at puberty, daily gain and probe backfat thickness. A total of 1,074 Select line, and 1,087 Control line gilts were included in the seven generations. Realized heritability of ovulation rate was 40 ± 7% based on the regression of response on weighted cumulative selection differential.

Regression of line difference (Select-Control) on generation number was —.13 ± .78 days, —.16 ± .47 kg, —.001 ± .003 kg/day and .01 ± .01 cm for age at puberty, weight at puberty, daily gain and probe backfat thickness, respectively. No significant correlated response was evident for any of the four traits.

Estimates of genetic correlation were obtained using the regression of direct and correlated response on weighted cummulative selection differential, realized heritability for ovulation rate, daughter-dam regression estimates of heritability, and pooled within line and generation standard deviations. Estimates obtained were —.04, —.06, —.13 and .09 between ovulation rate and age at puberty, weight at puberty, daily gain and probe backfat thickness, respectively. None of these estimates approached statistical significance.

¹ Published with the approval of the Director as Paper No. 5091, Journal Series, Nebraska Agr. Exp. Sta. Research reported was conducted under Project 13-1.

² Present address: Tri-Curry Farms, Atkinson, NE68713.

³ Department of Animal Science. The authors wish to express their sincere and deep appreciation to Mr. Roy Carlson for his tireless efforts in performing the critical estrus observations so necessary to the conduct of this study.

⁴ This research was supported in part by a cooperative agreement with the Agricultural Research Service, U.S.D.A.