Effect of level of chronic immune system activation on the lactational performance of sows.

The effect of the level of chronic immune system (IS) activation on sow lactational performance was determined in 11 pairs of littermate, primiparous sows. Sows with a low level of IS activation were created by rearing the animals via early weaning, isolated rearing schemes. During lactation, two levels of IS activation were achieved in each littermate sow pair by subcutaneous administration of either 0 (saline) or 5 microg/kg of sow BW of Escherichia coli lipopolysaccharide (LPS) in a mineral oil adjuvant emulsion on d 2 and 10 of lactation. Litters were standardized to 13 pigs by 8 h postpartum. Sows were offered daily 6.0 kg of a corn-soy diet formulated to contain a minimum of 250% of the dietary nutrient concentrations estimated to be needed by lactating sows. Based on antibody titers to LPS and serum concentrations of alpha-1 acid glycoprotein (AGP), high IS sows mounted an immune response to the LPS during lactation, and low IS sows maintained a low level of IS activation. Over an 18-d lactation, a high level of chronic activation of the sows' immune systems depressed daily sow feed intakes by .56 kg, litter weight gains by .32 kg, and daily milk by 1.4 kg, milk energy by 1.7 Mcal, and milk protein yields by 71 g, but did not alter sow body weight loss. The reductions in yields of milk and milk nutrients likely were because of proinflammatory cytokine-induced inhibition of the lactogenic hormones resulting from high chronic IS activation. Based on these data, the level of chronic IS activation alters the lactational performance of sows.