Abstract
Abstract Reproductive efficiency is critical to maximizing productivity in the swine industry. A recent study indicated that vulva score (VSC) assessed prior to puberty may be predictive of reproductive performance in sows, in which gilts with greater VSC had greater reproductive performance. The objective of this study was to validate the effect of VSC on reproductive performance, to estimate genetic parameters, and to perform genomic analysis of VSC. A total of 5494 phenotypes and 1326 genotypes (~50K SNPs) from two farms were available for this study. Measurements included VSC assessed using a three-point scale: small (VSC-S), medium (VSC-M), and large (VSC-L), at 15 and 14 weeks of age, for Farm 1 and 2, respectively, and subsequent first parity performance. Genetic parameters were estimated using single-step GBLUP. Genome-wide association study (GWAS) was performed for VSC using BayesB (p=0.999). For Farm1, VSC-L was associated with a greater (P-value=0.04) farrow rate (0.68±0.03) than VSC-S (0.53±0.07). For Farm2, VSC-L was associated with greater (P-value=0.04) number of piglets born alive (NBA; 11.4±0.17) and less mummified fetuses (P-value=0.03; 0.09±0.01) than VSC-S (10.9±0.14; 0.14±0.01). Heritability estimates of VSC were 0.35±0.06 for Farm1 and 0.34±0.05 for Farm2. Moderate genetic correlations between VSC with reproductive traits were found for total number born (0.61±0.21) and NBA (0.62±0.19). The GWAS identified multiple genomic regions associated with VSC. Of these, a QTL located on chromosome 1 at 85Mb accounted for >3% of the genetic variance. This region harbors ADAM21, a gene that has been associated with early embryonic development in pigs. These results validated the use of VSC for prediction of first-parity performance, identified genomic regions controlling VSC, and indicate that selection for increased VSC is possible and could improve reproductive efficiency in swine. We are grateful to Fast Genetics for providing the data and the Iowa Pork Industry Center for financial support.
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