Effect of boron supplementation of pig diets on the production of tumor necrosis factor-alpha and interferon-gamma

Two experiments were conducted to determine the effects of dietary B on the production of cytokines following an endotoxin challenge. In both experiments, pigs were obtained from litters generated from sows fed low-B (control) or B-supplemented (5 mg/ kg, as-fed basis) diets. In Exp. 1 and 2, 28 and 35 pigs, respectively (21 d old), remained with their littermates throughout a 49-d nursery phase and were fed either a control or B-supplemented diet. In Exp. 1, 12 pigs per treatment were moved to individual pens at the completion of the nursery phase and fed their respective experimental diet. On d 99 of the study, pigs were injected with 150 microg of phytohemagglutinin (PHA) to evaluate a local inflammatory response. Pigs receiving the B-supplemented diet had a decreased (P < 0.01) inflammatory response following PHA injection. Peripheral blood monocytes were isolated from six pigs per treatment on d 103 and cultured in the presence of lipopolysaccharide (LPS) to determine the effect of dietary B on tumor necrosis factor-alpha (TNF-alpha) production from monocytes. Isolated monocytes from pigs that received the B-supplemented diet had a numerically greater (P = 0.23) production of TNF-alpha. In Exp. 2, pigs were group housed with their littermates following the nursery phase for 43 d, after which 10 pigs per treatment were moved to individual pens. In Exp. 1 and 2, pigs were assigned randomly within dietary treatment to receive either an i.m. injection of saline or LPS on d 117 and d 109, respectively. The dose of LPS in Exp. 1 and 2 was 100 and 25 microg of LPS/kg of BW, respectively. In Exp. 1, serum TNF-alpha was increased (P < 0.01) at 2 h and tended to be increased (P < 0.11) at 6 and 24 h after injection by dietary B; however, only numerical trends existed for a B-induced increase in TNF-alpha in Exp. 2. Serum interferon-gamma (IFN-gamma) was increased (P < 0.01) at 6 h and tended to be increased (P < 0.08) at 24 h after injection in Exp. 1. In Exp. 2, dietary B also numerically increased IFN-alpha. These data indicate that dietary B supplementation increased the production of cytokines following a stress, which indicates a role of B in the immune system; however, these data do not explain the reduction in localized inflammation following an antigen challenge in pigs.