Performance Differences Between Two Groups Of Commercial Pigs Following Experimental Infection With Porcine Reproductive And Respiratory Syndrome Virus (Prrs) Virus 1-7-4

Abstract Porcine reproductive and respiratory syndrome virus (PRRSv) is the costliest swine disease of North America. Vaccines and management alone have not been effective at controlling this disease and genetic selection may be a complimentary approach to controlling PRRSv-infection. The objective of this study was to estimate performance differences between two groups of pigs from the same commercial line following infection with PRRSv 1-7-4: 1) pigs sired by boars selected based on a standard index (STD), which emphasizes feed efficiency and carcass quality; and 2) pigs sired by boars selected based on an experimental index (EXP), with emphasis on feed intake, piglet vitality, and robustness. Pigs (n~730 per group) were housed in a commercial research wean-to-finish barn. Average daily gain (ADG) and average daily feed intake (ADFI) were recorded from birth-to-slaughter. At weaning, pigs were placed in pens by group and balanced by sex. To facilitate collection of feed intake data, the experimental unit was pen, with 27 pens representing each group. Four weeks post-wean, all pigs were experimentally infected with 2mL of 1-7-4 PRRSv at 3.5 logs of TCID50 per mL. Statistical analyses were performed using a linear mixed model with group (STD or EXP) as a fixed effect and block as a random effect. No significant difference was detected between groups for wean-to-finish or 0 to 42 days post-infection (dpi) ADG. The ADFI was 0.06 kg/day greater for the EXP group than the STD group from 0 to 42 dpi (P = 0.01). Feed conversion ratio (FCR) was 0.03 (P = 0.03) less for the EXP group from wean-to-finish and 0 to 42 dpi, respectively. Pigs sired by boars selected using the experimental index showed no significant difference in ADG, but had greater ADFI post-challenge, while pigs sired by boars selected based on the standard index had significantly better FC.