Effect of health management strategy during rearing on grower-finisher pig performance and selected indicators of immune system stimulation

The effects of health management strategy during rearing on subsequent growth performance and indicators of immune system stimulation in grower-finisher (G-F) pigs were evaluated. Pigs of approximately 25 kg body weight (BW) were sourced from three different management systems: (1) a farrow-to-finish unit with identified respiratory problems (Conventional), (2) segregated early weaned (SEW; piglets sourced from multiple sow herds), and (3) a minimal disease farrow-to-finish operation (MD). The pigs were of similar genetic background and were housed under similar conditions until slaughter. During the grower phase, MD had the highest average daily gain (ADG) (P < 0.05), while it was similar for SEW and Conventional (P > 0.10). Feed to gain (F:G) was similar for MD and SEW (P > 0.10), and poorest for Conventional (P < 0.05). During the finisher phase, SEW had the lowest ADG, and the poorest F:G (P < 0.05); these parameters were similar for Conventional and MD (P > 0.10). Over the entire G-F period, performance of MD pigs was better than that of Conventional and SEW pigs. Performance depressions appeared related to the degree of anterior-ventral lung atelectasis, antibody titers to porcine reproductive and respiratory syndrome (PRRS) virus and Mycoplasma hyopneumoniae, thymus size, plasma insulin-like growth factor levels, stomach ulceration, nasal turbinate damage, and microbial burden. The current study shows that the growth depressing effects of exposure to infectious organisms can be substantial in G-F pigs.