Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 6/10/1996
Publication Date: N/A
Technical Abstract: Two selection lines derived from a common base population were crossed to make an F2 population to determine whether there is variation associated with single loci affecting ovulation rate, number of fully-formed, and number of mummified piglets. Line I was selected for increased ovulation rate and embryonic survival. Line C was a randomly selected control. Females of Line I exceeded females of Line C by 6.7 eggs ovulated and 3.1 fetuses at 50 d gestation after ten generations of selection. Five boars and 12 gilts with the highest index in Line I were crossed to 14 gilts and 5 boars with the lowest index in Line C to produce the F1 generation. The F1 were randomly mated for three parities to produce three replicates of F2 gilts. Fifty-five microsatellite markers were scored for 114 F2 females in the first replicate. Numbers of fully-formed and mummified pigs were recorded at first parity and ovulation rate was measured at their next estrus. The method of Haley et al. (1994) was used to calculate line-orig dominance effects of QTL. An animal model was fitted to the data from the first replicate. Additive genetic variance was held constant and a solution for residual variance was obtained iteratively. A QTL for ovulation rate was found on chromosome 8. The likelihood-ratio for this QTL was significantly different from zero at an experiment-wise error rate of P<.001. Evidence for other QTL was found for ovulation rate on chromosomes 4 (P<.1), 13 and 15 (P<.05) and on chromosome 14 for mummified pigs (P<.05). No strong evidence for QTL was found for fully-formed pigs. These results will be validated by using more markers to increase marker density and adding phenotypic measurements for replicates two and three.