Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/1997
Publication Date: N/A
Interpretive Summary: Evidence for QTL for ovulation rate was found on chromosomes 4, 8, 13, and 15. Effects on chromosomes 4, 13, and 15 must be interpreted with caution because threshold values exceeded the adjusted experiment-wise value of .001. Further study is required to determine if the QTL effects detected in this study are real. More markers and larger F2 populations are required to verify the effect and the location of the QTL. Data were analyzed with an animal model to describe the underlying biology for the traits and to account for relationships among records. There is a need for further refinement and study of statistical models and methods to analyze data from QTL mapping experiments with segregating populations. Development of such models will enhance application of marker-assisted selection.
Technical Abstract: Fifty-five microsatellite markers were scored in an F2 population of pigs (n=114 females) developed at the University of Nebraska. The population was produced by crossing a line previously selected for ten generations using an index of ovulation rate and embryonal survival and a line selected at random. The lines were from a common base population and differed by 6.7 eggs ovulated and 3.1 fetuses at 50 d of gestation. Ovulation rate, number of fully-formed pigs, and number of mummified pigs were recorded for each female. Data were analyzed with regression models that included random animal effects. Likelihood-ratio tests were used to test for QTL effects. The log-likelihood for the full model that included additive and dominance QTL effects was deviated from the log-likelihood for the reduced model that did not contain QTL effects. A QTL for ovulation rate was found on Chromosome 8 with an additive effect of 3.07 ova. Other evidence of QTL affecting ovulation rate was found on Chromosome 4, 13, and 15. Effects on Chromosomes 4, 13, and 15 were not significant for an experiment-wise threshold value of P < .001. No significant QTL for litter size or number of mummified pigs were found. Additional data are needed to confirm the location and the effect of QTL found for ovulation rate before markers associated with them are used in marker-assisted selection.