Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/1998
Publication Date: N/A
Citation: Interpretive Summary: Infection with viral, bacterial, and protozoan agents can induce chronic activation of the immune system. A consequence of activation of the immune system is the production of a family of proteins referred to as cytokines. These proteins are produced by a variety of cells comprising the immune system. Some of these proteins, referred to as inflammatory cytokines, are responsible for the elevated metabolism and temperature observed in the animal during an infection. In food-production animals, it has been suggested that the indirect effects of continual production of these proteins during chronic exposure to disease-causing agents are reduced feed intake and growth rates, and altered composition of the body. These changes are costly to the producer. The present study evaluated effects of experimentally-induced chronic activation of the immune system in lactating sows on feed intake, body weight change, backfat change, litter weight gain, and milk yield and composition. Results from the study indicate the chronic activation of the immune system of lactating sows depresses their feed intake and milk production, and alters milk composition. Efforts to minimize chronic activation of the immune system by infectious agents may benefit the performance of lactating sows.
Technical Abstract: The impact 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. Two levels of IS activation were achieved in each littermate sow pair by subcutaneous administration of either O (saline) or 5 ug/kg sow BW of E. coli lipopolysaccharide (LPS) in a mineral oil adjuvant emulsion on days 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 the lactating sow (NRC 1988). 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 while low IS sows maintained a low level of IS activation. Over the 18-day lactation, a high level of chronic activation of the sow's immune system depressed daily sow feed intakes by .56 kg, litter weight gains by .32 kg and daily milk, milk energy, and milk protein yields by 1.4 kg, 1.7 Mcal, and 71 g, respectively, but did not alter sow body weight loss. The reductions in yields of milk and milk nutrients were likely due to 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.