Submitted to: Animal Genetics International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1998
Publication Date: N/A
Technical Abstract: Because litter size is an important trait to the swine industry, a multi- generation crossbred Meishan-White composite resource population was developed to identify QTL for the components of litter size, ovulation rate (number of ova shed in an estrous period) and uterine capacity. The population was established by reciprocally mating Meishan (ME) and White composite (WC) pigs. The resultant F1 females were mated to either ME or WC boars to produce backcross progeny (BC) of either 3/4 WC 1/4 ME or 1/4 WC 3/4 ME. To produce the next generation (F3), 3/4 WC 1/4 ME animals were mated to 1/4 WC 3/4 ME animals yielding half-blood (1/2 WC 1/2 ME) progeny. A final generation (F4) was produced by inter se mating half-blood animals. Ovulation rate was determined by counting the number of corpora lutea in 101 BC, 389 F3 and 110 F4 gilts at approximately eight months of age. A genomic scan was conducted with markers (n=157) spaced ~20 cM apart. All of the parental, F1 and BC generation animals were genotyped, along with 84 F3 and 110 F4 animals with phenotypic measurements. A least-squares regression analysis was conducted fitting a QTL at 1 cM intervals throughout the genome. Approximate genome-wide significance levels were computed to adjust for the number of tests conducted. A significant [P(false positive) <.05] QTL was detected on chromosome 8 and a suggestive [P(false positive) < 1.0] QTL was detected on chromosome 9. Two additional regions were detected which potentially possess a QTL [P(false positive) < 2.0] on chromosomes 3 and 10. Additional genotypes need to be collected to determine the level of significance for each region and the genotypic means for each QTL genotype. Further analyses are continuing on other populations of swine with diverse ovulation rates.