Effects Of Alfalfa Polysaccharides On The Growth Performance Of Piglets And Its Mechanisms

The present study was conducted to investigate the effects of alfalfa polysaccharides(APS) on the growth performance of piglets and its mechanisms. A total of 30 piglets(initial body weight of 15.76 ± 0.81 kg) in good body conditions were randomly allotted to 5 dietary treatments(basal diet supplemented with 0, 300, 500, 800 or 1200 mg/kg APS) with 6 replications per treatment. The experiment was conducted for 49 d, including adjustment period for 7 d and formal experiment period for 42 d. Piglets were given free access to water and feed throughout the entire experimental period. 1200 mg/kg APS significantly reduced average daily gain(ADG) and triggered severe diarrhea, which severely influenced the growth performance of piglets. Compared with the control, supplementation of 500 or 800 mg/kg APS significantly increased(P < 0.05) ADG and feed conversion rate(FCR) without influencing average daily feed intake(ADFI)(P > 0.05). Piglets fed 500 or 800 mg/kg APS had higher spleen index and liver index than those in control(P < 0.05). Lymphocyte count in serum was increased(P < 0.05) at the 300 or 500 mg/kg APS inclusion level. Dietary supplementation of 500 or 800 mg/kg APS resulted in an increase in serum albumin level and a decrease in blood glucose level(P < 0.05). Piglets in APS groups had lower(P < 0.05) serum total cholesterol level than the piglets in control. Compared with the control, supplementation of 500 mg/kg APS significantly reduced(P < 0.05) serum aspartate aminotransferase(AST) level. Piglets fed APS at 300, 500 or 800 mg/kg had greater(P < 0.01) numbers of lactobacilli in the cecum and colon and lower(P < 0.01) numbers of of escherichia coli and salmonella in the cecum, colon and rectum than piglets fed the control diet. Dietary supplementation of APS at 500 or 800 mg/kg increased(P < 0.01) numbers of lactobacilli in the rectum. Diets with either 500 or 800 mg/kg APS increased(P < 0.01) villus height in the duodenum. Piglets fed APS had higher(P < 0.05) villus height and villus height to crypt depth ratio in the jejunum than piglets fed the control diet. Supplementation of APS at 500 or 800 mg/kg APS reduced(P < 0.01) crypt depth in the jejunum compared with the control diet. 500 mg/kg APS reduced(P < 0.01) ileal villus height. Supplementation of APS at 500 or 800 mg/kg APS significantly reduced(P < 0.01) crypt depth and improved villus height to crypt depth ratio in the ileum. Supplementation of APS significantly increased(P < 0.01) activities of trypsin and amylase in the duodenum and jejunum and amylase activity in the ileum. There was a significant increase(P < 0.05) in trypsin activity at 500 mg/kg inclusion level in the ileum. Compared with the control, supplementation of APS at 500 or 800 mg/kg decreased(P < 0.05) the serum diamine oxidase(DAO) level. Supplementation of APS significantly increased(P < 0.05) DAO level in the jejunum and ileum compared with the control. There were no significant differences(P > 0.05) among treatments in the tumor necrosis factor-?(TNF-?) and interleukine-1?(IL-1?) mRNA relative expression in the duodenum. Compared with the control, supplementation of 500 or 800 mg/kg APS reduced(P < 0.05) TNF-? and IL-1? mRNA relative expression in the jejunum and TNF-? mRNA relative expression in the ileum. Piglets fed 500 mg/kg APS had lower(P < 0.05) IL-1? mRNA relative expression than piglets fed the control diet, 300 or 800 mg/kg APS. Duodenal occludin mRNA relative expression of piglets fed 500 or 800 mg/kg APS were increased(P < 0.05) compared with the control. An increased of occludin mRNA relative expression in the jejunum of piglets in 500 mg/kg APS group was observed(P < 0.05). Supplementation of 500 or 800 mg/kg APS increased mucin 2(MUC2) mRNA relative expression in the jejunum. Dietary supplementation of APS increased(P < 0.05) occludin mRNA relative expression in the ileum compared with the control. Piglets fed 500 or 800 mg/kg APS had greater(P < 0.05) zonula occludens-1(ZO-1) and MUC2 mRNA relative expression than the control. In conclusion, supplementation of APS at 500 or 800 mg/kg could improve the growth performance of piglets by increasing ADG and FCR. However, excessive concentrations of APS had negative effect on the growth performance. The mechanisms of APS improving the growth performance were that: APS enhanced immunity by improving the immune organs index and reducing proinflammatory cytokines mRNA expression; APS improved intestinal microflora, digestive enzyme activities, morphology and barrier function.