Metabolic inflammation and immunomodulation in transition dairy cows

Abstract Text: The transition period in dairy cows is characterized by dramatic increases in nutrient requirements for lactation and substantial metabolic stress. The disturbed metabolic balance, coupled with suppressed immune function, contributes to markedly elevated incidence of health disorders. Several lines of evidence suggest that increased inflammation is common during the transition period. Unlike the classical inflammation associated with acute infection, the postpartum inflammatory state is low-grade and often of metabolic origin. This metabolic inflammation plays a key role in numerous disorders; an improved understanding of inflammatory pathways in transition cows may improve our ability to predict and prevent disorders. To mimic metabolic inflammation, we administered low concentrations of recombinant bovine tumor necrosis factor-α (rbTNFα), a pro-inflammatory cytokine, to early lactation cows, and evaluated whether rbTNFα affects milk production, metabolism, and health. We found that rbTNFα administration increased plasma concentrations of TNFα and haptoglobin, indicating increased systemic inflammation. As a family of molecules produced by fatty acid oxidation, eicosanoids play key roles in inflammatory signaling. We found that although most plasma eicosanoids were not affected by rbTNFα administration, 6 out of 16 measured eicosanoids changed over the first week of lactation, reflecting elevated pro-inflammatory mediators in the days immediately following parturition. Dry matter and water intake, milk yield, and milk fat and protein yields were all decreased by rbTNFα treatments by 15 to 18%. Administration of rbTNFα did not affect energy balance or markers of glucose and lipid metabolism, but increased the incidence of ketosis by 3-fold in the first week of lactation. These data suggest that low-grade inflammation may impair production independent of altering systemic metabolism. Conversely, preventing excessive inflammation has the potential to improve productivity and health of dairy cows. To identify nutritional strategies that could enhance metabolism and immunity, we have also evaluated the efficacy of several feed additives, including niacin, chromium propionate, and yeast, in early lactation. Overall, a greater understanding of the role of metabolic inflammation in early lactation and the nutritional strategies that could modulate these signals may improve the production and health of dairy cows.

Keywords: inflammation, metabolism, transition dairy cow