Identification of quantitative trait loci affecting female reproductive trails in a multigeneration Meishan-White composite swine population

A multigeneration crossbred Meishan-White composite resource population was used to identify quantitative trait loci (QTL) for age at first estrus (AP ) and the components of litter size: ovulation rate (OR; number of ova rele ased in an estrous period) and uterine capacity (UC). The population was es tablished by reciprocally mating Meishan (ME) and White composite (WC) pigs . Resultant Fl females were mated to either ME or WC boars to produce backc ross progeny (BC) of either 3/4 WC 1/4 ME or 1/4 WC 3/4 ME. To produce the next generation(F-3), 3/4 WC 1/4 ME animals were mated to 1/4 WC 3/4 ME ani mals yielding half-blood (1/2 WC 1/2 ME) progeny. A final generation (F-4) was produced by inter se mating F-3 animals. Measurements for AP and OR wer e recorded on 101 BC, 389 F-3, and 110 F-4 gilts, and UC data were from 101 BC and 110 F-4 first parity litters. A genomic scan was conducted with mar kers (n = 157) spaced similar to 20 cM apart. All parental, F-1, BC, and F- 4 animals but only 84 F-3 animals were genotyped and included in this study . The QTL analysis fitted a QTL at 1-cM intent als throughout the genome, a nd QTL effects were tested using approximate genome-wide significance level s. For OR, a significant (E[false positive] < .05) QTL was detected on chro mosome 8, suggestive (E[false positive] < 1.0) QTL were detected on chromos omes 3 and 10, and two additional regions were detected that may possess a QTL (E[false positive] < 2.0) on chromosomes 9 and 15. Two regions possesse d suggestive evidence for QTL affecting AP on chromosomes 1 and 10, and one suggestive region on. chromosome 8 was identified for UC. Further analyses of other populations of swine are necessary to determine the extent of all elic variation at the identified QTL.