Studies On The Effects Of Glutamine On Relieving Weaning Stress And The Mechanism In Weaned Calves

This study aimed to investigate the effects of dietary supplementation with glutamin (Gin) on the growth performance, immune performance, antioxidation, intestinal structure and autophagy of liver cells and intestinal epithelial cells in weaned calves, and studied the mechanism which protected the calf from weaning stress in celluar level.Experiment 1 The effects of Gin on the growth performance and blood biochemical indicators in weaned calves.Thirty newborn Holstein bull calves, at 38±2.0 kg of BW, were selected for this study. At 35 d of age, 30 calves were randomly assigned to 5 treatments based on BW and date of birth. Between 43 and 70 d of age (2 weeks before and after weaning), calves were fed daily rumen protected L-Glutamine (L-Gln) of 0 (control group),1%,2%,3%, and 4% of calf starter intake. The L-Gln content of rumen protected L-Gln is 50%. The rumen degradation rate and small intestine release rate of rumen protected L-Gln were 25% and 87%, respectively.The results indicated that weaning significantly decreased the ADG (P<0.05) and significantly increased the DM1 and feed convention rate (P<0.05). Different levels of Gin significantly increased the average daily gain (ADG) and dry matter intake (DMI) (P<0.01), but had no significant effect on feed convention rate (.P>0.05). The 1% treatment had the most ADG, DMI and feed convention rate. Weaning significantly decreased the concentration of glucose and Gin and significantly increased urea N concentration in blood (P<0.05). Different levels of Gin had no effect on the concentration of glucose in blood, but significantly increased the Gin and urea N concentration in blood (P<0.05). Weaning significantly increased the growth hormone concentration and significantly decreased insulin concentration in blood (P<0.01). Different levels of Gin had no effect on the concentration of insulin and growth hormone in blood (P>0.05).Experiment 2 The effects of Gin on the immune performance and atioxidation in weaned calves.This experiment has same experiment design with experiment 1. Weaning significantly decreased the abundance of CD3+ and CD14+ in blood (P<0.05). Different levels of Gin increased the abundance of CD4+,CD8+, CD14+and the ratio of CD4+/CD8+in blood, but have no significant difference (P>0.05). Weaning significantly decreased the concentration of IgG (P<0.05), but had no effect on the concentration of IgM and IgA in blood (P>0.05). Different levels of Gin significantly increased the concentration of IgG and IgM in blood (P<0.05), and had no effect on the concentration of IgA in blood (P>0.05). Weaning significantly decreased the GSH-Px activity and the T-AOC (P<0.05), but had no effect on the CAT, T-SOD and MDA activity (P<0.05). Different levels of Gin significantly increased the GSH-Px activity and the T-AOC (P<0.01), but had no effect on the CAT and T-SOD activity (P<0.05).Experiment 3 The effects of Gin on the intestinal structure in weaned calves.Six calves per treatment were slaughtered at 70 d of age. The intestinal tissue samples were collected and fixed in 10% formaldehyde. The villus height and crypt depth of duodenum, jejunum and ileum and the ratio of villus height to crypt depth were detected. The reslts showed that different levels of Gln had no effect on the villus height and crypt depth of duodenum, jejunum and ileum and the ratio of villus height to crypt depth (P>0.05). The 1% treatment had the highest villus height and crypt depth of duodenum, jejunum and ileum and the maximal ratio of villus height to crypt depth.Experiment 4 The effects of Gln on the autophagy in liver cells and in intestinal epithelial cells.Six calves per treatment were slaughtered at 70 d of age. Liver and jejunum tissue samples were collected for detecting the autophagy in liver cells and in intestinal epithelial cells by western blotting. The results showed that different levels of Gln increased the autophagy level of liver cells, and the 3% treatment significantly increased the autophagy level of liver cells (P<0.05). Different levels of Gln significantly decreased the autophagy level of intestinal epithelial cells (P<0.05), and the 1% treatment had the lowest level of autophagy in intestinal epithelial cells. Dietary supplementation with glutamin can regulate autophagy of liver cells and intestinal epithelial cells by PI3k/AKT, S6K1, and P38MAPK signaling pathways.