Selection for Ovulation Rate in Swine: Population, Procedures and Ovulation Response

Abstract

Five generations of selection for ovulation rate in swine have been applied in a multi-breed synthetic line of swine. Corpora lutea were counted on 845 gilts in each of two lines. Mass selection was practiced for number of corpora lutea in one line with the other line serving as a control. Inbreeding levels were less than 1% and similar for both lines. Mean ovulation rates were 14.4 for the Select line vs 14.6 for the Control line in generation 0 and 16.2 vs 13.7 in generation five. The regression of line mean on generation number was .40 ± .09 for the Select line and -.16 ± .05 for the Control line. Realized heritability was estimated by three methods. Estimates obtained were 52 ± 10% from conventional regression of response on cumulative selection (Method 1), 40 ± 8% when response deviations from controls were weighted by cumulative selection differentials (Method 2) and 45 ± 7% from Fifth generation only (Method 3). Copyright © 1975. American Society of Animal Science . Copyright 1975 by American Society of Animal Science.