Effects of Achyranthes bidentata polysaccharide on growth performance, immunological, adrenal, and somatotropic responses of weaned pigs challenged with Escherichia coli lipopolysaccharide

A study was conducted with 48 weaned barrows (28 +/- 3 d, 8.45 +/- 0.14 kg) to determine the effect of Achyranthes bidentata polysaccharide (ABPS) supplementation on pig performance, immunological, adrenal and somatotropic responses following Escherichia coli lipopolysaccharide (LPS) challenge. The experiment was a 2x2 factorial design; the main factors included diet (supplementation with 0 or 500 mg/kg ABPS) and immunological challenge (LPS or saline). On d 14 and 21 of the trial, pigs were given an intraperitoneal injection with either 100 mu g/kg BW of LPS or an equivalent amount of sterile saline. Blood samples were obtained 3 h after injection for analysis of tumor necrosis factor-alpha (TNF-alpha), prostaglandin E-2 (PGE(2)), cortisol, growth hormone (GH), insulin-like growth factor (IGF)-I and immunoglobulin G (IgG). On d 2 after LPS challenge, peripheral blood lymphocyte proliferation (PBLP) was measured. LPS administration decreased average daily feed intake (ADFI) (p < 0.05), had a tendency to decrease average daily gain (ADG) (p < 0.10) during both the first and second challenge periods and increased (p < 0.05) feed:gain ratio only during the first challenge period. ABPS tended to improve ADG (p < 0.10) during the first challenge period, and improved ADG (p < 0.05) and tended to improve ADFI (p < 0.10) during the second challenge period. ABPS did not affect feed:gain ratio. An interaction (p < 0.05) between LPS challenge and diet was observed for the plasma concentrations of TNF-alpha, PGE2 and cortisol after both LPS challenges such that, among LPS-treated pigs, pigs fed the ABPS diet were lower for these indices than those receiving the control diet. In contrast, pigs fed the ABPS diet had higher IGF-I (p < 0.05) compared with those fed the control diet. No effect of diet, LPS challenge or both on GH and IgG was observed after both LPS administrations. LPS challenge increased PBLP when these cells were incubated with 8 mu g/ml of LPS during both the challenge periods, and did likewise when incubated with 8 mu g/ml of concanavalin A only after the first challenge. ABPS had no effect on PBLP. These data demonstrate that ABPS alters the release of pro-inflammatory cytokines following an immunological challenge, which might enable pigs to achieve better performance.