Effects of [beta]-glucan extracted from Saccharomyces cerevisiae on growth performance, and immunological and somatotropic responses of pigs challenged with Escherichia coli lipopolysaccharide

Three experiments were conducted to investigate the effects of [beta]-glucan supplementation on pig performance and immune function. In Exp. 1, 100 weaned pigs (8.65 [+ or -] 0.42 kg of BW and 28 [+ or -] 2 d of age) were used in a 35-d experiment to determine the effects of graded levels of [beta]-glucan. Pigs were randomly allotted to 1 of 5 treatments containing [beta]-glucan supplemented at 0, 25, 50, 100, or 200 ppm. Each treatment was replicated using 5 pens containing 4 pigs per pen. The ADG of pigs between d 14 to 28 and d 0 to 28 responded to dietary [beta]-glucan in a quadratic fashion (P < 0.05), whereas [beta]-glucan had no effect on ADFI and G:F in any period. In Exp. 2, 80 crossbred pigs (8.23 [+ or -] 0.56 kg of BW and 28 [+ or -] 2 d of age) were used in a 35-d experiment. Pigs were allotted to 1 of 2 dietary treatments (0 or 50 ppm of [beta]-glucan in the diet) using 10 pens with 4 pigs per pen. Pigs treated with [beta]-glucan had greater ADG in the 14- to 28-d (P = 0.05) and 0-to 28-d (P = 0.035) periods. The ADFI of pigs receiving [beta]-glucan was increased (P < 0.05) in the periods from 0 to 14, 0 to 28, and 28 to 35 d. The lymphocyte proliferation index in response to phytohemagglutinin (P = 0.051) and concanavalin A (P = 0.052) tended to decrease on d 14 in pigs supplemented with [beta]-glucan compared with pigs without supplementation. In Exp. 3, 24 barrows (8.89 [+ or -] 0.20 kg of BW and 28 d of age) were used to investigate the immunological and somatotropic responses of pigs challenged with lipopolysaccharide (LPS). Experimental treatments were arranged in a 2 x 2 factorial, with the main effects of LPS challenge (saline vs. LPS) and dietary addition of [beta]-glucan (0 vs. 50 ppm). Pigs were raised individually in metabolic cages. Pigs were fed 0 or 50 ppm of [beta]-glucan for 28 d and then challenged with LPS (25 [micro]g/kg of BW) or saline. After LPS injection, blood was obtained at 0, 1.5, 3, 4.5, 6, and 7.5 h to determine cytokine production and the somatotropic response. Dietary [beta]-glucan increased plasma interleukin-6 at 1.5, 3, and 4.5 h and tumor necrosis factor-[alpha] at 3 and 4.5 h and increased plasma interleukin-10 from 3 to 7.5 h after LPS challenge. The [beta]-glucan treatments had no effect on growth hormone. In conclusion, [beta]-glucan can selectively influence performance and partially offer benefits on somatotropic axis and immune function in weaned piglets challenged with LPS. Key words: beta-glucan, performance, immunity, lipopolysaccharide, piglet