Molecular Breeding Value Prediction Of Vaccination Response Against Porcine Reproductive And Respiratory Syndrome (Prrs) In Replacement Gilts

Abstract Porcine reproductive and respiratory syndrome (PRRS) is a viral disease that severely affects the Mexican swine industry. Vaccination of replacement gilts is mostly used to prevent PRRS; however, individual response to this protocol is highly-variable. The objective herein was to predict vaccination response against PRRS virus in gilts using molecular markers associated to rectal temperature (RT) and average daily weight gain (ADG). The study included 6-month old replacement gilts (n = 100) with a breed composition of ¾ Landrace x ¼ Yorkshire. Gilts were vaccinated with a modified live PRRS-virus (day 0) and kept inside the quarantine area on a farm where the gilts were lately exposed to PRRS. Data from RT and ADG were recorded weekly from day -7 through 35. Individual blood samples were collected at day 40, spotted onto FTA cards, and processed for genomic analyses using a 10k low-density SNP chip. Resulting genotypes were analyzed using a multi-locus mixed model, which identified 59 SNP associated with RT and ADG. These SNP were validated using a mixed-effects model which included SNP genotype and age of dam as fixed effects, and sire as random effect; then, their allele substitution effects were calculated. The additive effects for each SNP that showed a significant association (P < 0.05) with either RT or ADG were summed to calculate their corresponding molecular breeding value (MBV). The mean MBV were 0.28±0.04°C and 0.21± .05kg for RT and ADG, respectively. A reduced regression model which only included MBV was used to predict both RT and ADG. Coefficients of determination were 4.26 and 3.87% for RT and ADG, respectively (P < 0.01). These results suggest that only a small proportion of the phenotypic variance for RT and ADG was explained by SNP genotypes. We suggest additional studies to determine if the highly-variable vaccination response to PRRS is influenced by genetics.