| This experiment was conducted to study the effects of dietary glutamine on the growth performance and immunity of weanling piglets and approach to its promoting mechanism in terms of intestinal digestive enzyme, intestinal morphology and endocrine hormone levels and its improving immune function mechanism in terms of DNA contents, gene expression, T lymphocyte proliferation and differentiation.One hundred and twenty piglets weaned at 21 days (Duroc×Landrace×Yordshire) were randomly allotted to four groups, each of which was replicated three times with ten pigs per replicate. The groups received the same basal diet, supplemented with 0,0.5%,1.0%,1.5% glutamine, respectively for 21 days. All pigs were given ad libitum access to feed and water. Six piglets on the 10th and 20th day of preweaning and postweaning periods in each group were weighed and slaughtered, at the same time samples were collected for analysis.The results were as follows:The diarrhea ratio supplementation with glutamine was significantly reduced as compared with the control at the 9th day and no diarrhea was happened at the 12th day, while the control group had higher diarrhea ratio. The diarrhea ratio was fifty to sixty percent on the 8-11th day of postweaning period, twenty to thirty percent on the 12-15th day.The results of feeding trial showed that on the 10th day of postweaning period, consumption of 0.5%,1.0%and 1.5%glutamine decreased feed conversion by 14.00%(P＜0.05),12.05% P＜0.05) and 9.13%(P>0.05), as compared with the control, respectively. While pigs fed with glutamine had greater ADG than the control, the tendency was not significant. Supplementation with 0.5,1.0,1.5%glutamine increased ADG by 21.39%(P>0.05),27.75%(P＜0.05) and 12.72%(P>0.05) in the second ten days, respectively.Consumption of 1.0%glutamine reduced uric nitrogen by 17.36%(P>0.05) and 4.26% (P>0.05) respectively on the 10th and 20th day of postweaning as compared with the control. Adding Glutamine had no effect on serum total protein on the 10th day and increased by 18.70% (P>0.05) on the 20th day of postweaning period, as compared with the control. Adding glutamine had no effect on serum albumin, T3 and T4 levels, but increased growth hormone levels by 12.18%(P>0.05) and 14.93%(P>0.05), respectively, on the 10th and 20th day of postweaning period.Compared with the control in 1th day of postweaning, the activities of total protease and chymotrypsin in duodenal content were decreased by 8.24%(P>0.05),4.63%(P>0.05) and 32.42%(P＜0.05),27.26%(P<0.05),respectively in control and 1%glutamine group on the 10th day of postweaning period. Supplementation with glutamine increased the activity of trypsin in duodenal content by 25.87%(P＜0.05) on the 10th day of postweaning period, and increased the activities of total protease, chymotrypsin and trypsin in duodenal content by 12.83%(P＜0.05), 16.31%(P>0.05) and 26.08%(P＜0.05), respectively, on the 20th day of postweaning period.The thickness of duodenal wall lamina propria, jejunal villus height and crypt depth on the 10th day of postweaning period were significant affected (P＜0.05) supplementation with 1.0% Glutamine. The duodenal villus height, thickness of duodenal wall lamina propria, jejunal villus height and crypt depth on the 20th day of postweaning period were significant affected (P＜0.05) supplementation with Glutamine.As compared with the control in the first ten days, the serum IgG and IgM concentrations in control and 1.0%glutamine supplementation group were decreased by 17.94%(P>0.05) and 31.26%(P＜0.05),11.43%(P>0.05) and 13.69%(P＜0.05), respectively, than that of preweaning. The IgA levels of the control and 1.0% Glutamine supplementation group were 20.31%(P>0.05) and 28.13%(P＜0.05) higher than that of preweaning. The IgG and IgM concentrations of serum in 1.0% Glutamine supplementation group were 6.49%(P>0.05),35.04%(P＜0.05) and 32.58% (P<0.05) higher than that of the control group, respectively. The analysis of serum parameters showed that adding 1%glutamine increased IgA, IgG and IgM by 6.49%(P>0.05),7.94% (P>0.05) and 25.56%(P＜0.05), respectively, as compared with the control. It also increased the serum C3, IL-2 and IL-6 contents by 38.57%(P<0.05),23.81%(P<0.05) and 36.36%(P<0.05), respectively.In the second ten days, supplementation with 1.0%Glutamine increased serum IgA, IgG and IgM concentrations by 8.06%(P>0.05),11.13%(P<0.05) and 11.93%(P<0.05), respectively, than that of control. The serum C3 was increased by 25.61%(P>0.05) than that of control group, as well as IL-2, IL-6 by 31.92%(P<0.05) and 66.67%(P<0.05), respectively. Glutamine supplementation significantly increased the ratio of T lymphocyte proliferation and differentiation by 75.08%(P<0.05) in vitro. Supplementation with 1.0%glutamine increased the mesenteric lymph and jejunal DNA content by 9.18%(P<0.05) and 12.59%(P＜0.05), respectively, than that of control.The results of antioxidant enzyme activity in liver and cytokine concentration in lymph organizations were as follows:1) The GSH-Px enzyme activity of liver in 1%glutamine supplementation group was 11.87%(P<0.05) and 9.56%(P<0.05) higher than the control group in the first and second ten days, respectively. The SOD enzyme activity in 1%glutamine group was decreased by 6.93%(P>0.05),9.54%(P<0.05) in the first and second ten days, respectively. 2) The IL-2 and IL-6 concentrations of lymph in 0.5%glutamine supplementation group were increased by 10.39%(P>0.05) and 11.68%(P>0.05) than that of control in the first ten days, as well as 13.14%(P<0.05) and 8.33%(P>0.05) in the second ten days than that of control.DNA fragments of SOD, GSH-Px and IL-6 were cloned using the special primers of SOD, GSH-Px and IL-6 designed, respectively, according to the reported porcine SOD, GSH-Px and IL-6 gene sequences. The analysis of obtained fragment suggested that 99%homology of all the three genes compared with that of the reported cDNA sequence (E06791, AF532927 and M80258) in Genebank.The results of RT-PCR showed that:1) the SOD mRNA in dietary glutamine group was decreased by 47.94%(P>0.05) and 77.02%(P<0.05) than that of the control in the first and second ten days, respectively.2) Adding glutamine increased the GSH-Px mRNA by 73.16% (P<0.05) and 28.27%(P>0.05) as compared with the control group in the first and second ten days, respectively.3) The IL-6 mRNA in glutamine supplementation group was increased by 200.1%(P<0.05) and 136.18%(P<0.05) than that of the control in the first and second ten days, respectively.The results of this study implicated that glutamine played very important role in the immunity system of early-weanling piglets. Supplementation with glutamine could promote the T lymphocyte proliferation and differentiation and regulate the mRNA expression of the immunity concerning genes, therefore enhanced the immunity function of weanling piglets in terms of serum immune globulin, antioxidant enzyme activities of liver and contents of serum cytokine, and improved the intestinal mucosal morphology.
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