Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 7, 1998
Publication Date: N/A
Interpretive Summary: This study represents the first report on mapping QTL for the components of litter size using a genome wide scan. Most of the traits analyzed are impractical for producers to measure, so marker assisted selection may be a more practical approach to be used by the industry. In addition, litter size is one of the most economically important traits to producers and traditional selection results in only marginal improvements. The identified genomic regions for traits affecting litter size need to be examined in commercial swine populations to determine if allelic variation at the QTL exists. Such specific information will significantly help the swine industry develop effective genetic improvement programs for litter size.
Technical Abstract: A multi-generation crossbred Meishan-White composite resource population was developed to identify quantitative trait loci (QTL) for age at first estrus (AP) and the components of litter size: ovulation rate (OR; number of ova released in an estrous period) and uterine capacity (UC). The population resulted from a cross of Meishan (ME) and White composite (WC) pigs. 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. For the next generation (F3), 3/4 WC 1/4 ME animals were mated to 1/4 WC 3/4 ME animals. A final generation (F4) was produced by inter se mating F3 animals. Measurements for AP and OR were recorded on 101 BC, 389 F3 and 110 F4 gilts and UC data were from 101 BC and 110 F4 first parity litters. A genomic scan was conducted with markers (n=157) spaced approximately 20 cM apart on all phenotyped animals excluding 305 F3 females. A regression QTL analysis was implemented and significance levels converted to approximate genome-wide values. For OR a significant [E(false positive) <.05] QTL was detected on chromosome 8, suggestive [E(false positive) < 1.0] QTL were detected on chromosomes 3 and 10 and two additional regions were detected which potentially possess a QTL [E(false positive) < 2.0] on chromosomes 9 and 15. Two regions possessed suggestive evidence for QTL affecting AP on chromosomes 1 and 10; while one suggestive region on chromosome 8 was identified for UC. Studies on other populations of swine are necessary to develop industry applications for identified QTL.