Effects of porcine reproductive and respiratory syndrome virus infection on the performance of commercial sows and gilts of different parities and genetic lines

Objectives: To examine the parity and genetic-line differences and trends for major sow reproductive traits during an outbreak of porcine reproductive and respiratory syndrome (PRRS) and to determine whether specific parities or genetic lines are more severely affected by PRRS virus. Materials and methods: Reproductive performance data (gestation length, total piglets in utero, total piglets born alive, total piglets born dead, total mummified piglets born, total stillborn, and total weaned) were obtained from a commercial herd in China (8098 litters from 1820 sows) from differing genetic lines (Landrace, Large White, Pietrain, Meishan, Duroc composite, and various crosses). The dataset was partitioned into a baseline and a disease phase. Statistical analysis compared performance differences between these two phases for sows of different parities and lines. Results: PRRS caused significant production losses, impacting most reproductive traits. However, the impacts were greater in early parities, eg, the numbers of mummified piglets per litter were greater for sows of lower parities (1 through 5) than older sows (parities 6 through 11), for which there were no differences between disease and baseline data. Line différences and interactions were also detected, highlighting a greater impact of PRRS virus on the Meishan line than on their European counterparts. Implications: Parity should be considered when examining host genetic resistance to PRRS virus and when designing management strategies. The Meishan line may be more susceptible to reproductive PRRS. The use of the Meishan-type line to impact fecundity traits in a disease situation should be reconsidered.