| Since digestive physiology has not yet mature in infant, infants often show a series of negative phenomena after weaning or food changes that can lead to intestinal stress and damage intestinal function. These changes will result in body with lacking adequate intake of nutrients and energy and seriously restricts the healthy development of the body. In post-weaning pigs, an experimental model is considered as more relevant for human physiological characteristics and nutritional metabolism characteristics. Thus we select the weaned piglets as experimental animal models in this study. The present study was conducted to analyze the changes of weaned piglets’ some indexes at different stages with tryptophan supplementation,including the growth performance, the serum biochemical indexes, the activity of antioxidative enzymes, the levels of mRNA and protein, the content of free amino acids and catabolic enzymes of tryptophan, the expression of amino acid transporter.It aimed to explore the protective effect of tryptophan on intestinal injury of weaned piglets. The results of ths study not only has very important significance to promote healthy piglets growth and obtain better quality of meat quality, but also have certain reference value to improve infant nutrition.Methods: A total of 42 piglets(offspring of Duroc × Landrace ×Yorkshire) with body weight(BW) of 6.88±0.205 kg were weaned in 21 days from birth and were assigned randomly to three treatment groups(n = 7 per group). In control group, the piglets were fed on a corn and soybean meal-based diet(containing 0.1 % Trp),whereas Trp groups(0.1 or 0.2 % Trp) were fed with the basal diet plus 0.1 or 0.2 %Trp, respectively. At the end of the experiment, we obtained the blood samples of the weaned piglets at 8:00 a.m on the 8th and 15 th days after 12 h lasting.(1) The results showed that a moderate amount supplementation of Trp in diet significantly increased(P < 0.05) the ADG and ADFI of the weaned piglets in 7d.Trp supplementation increased(P < 0.05) the contents of glucose and albumin while decreased the content of cholesterol. Supplying Trp decreased(P < 0.05) the contents of urea N and triglyceride. In addition, a moderate amount supplementation of Trpin diery significantly increased(P < 0.05) the ADG, ADFI and F:G of piglets in 14 d.Trp supplementation increased(P < 0.05) the activity of ALP and the content of ALB.Trp decreased the activity of ALT and the contents of CHO, Urea N, TG, TBIL, LDL and HDL.(2)The results showed that supplying a moderate amount of Trp in diet significantly increased(P < 0.05) the T-AOC and superoxide dismutase(SOD)activity, and reduced(P < 0.05) Malondialdehyde(MDA) level in 7d. Trp increased total antioxidant capacity(P < 0.05). Furthermore, dietary Trp up-regulated(P < 0.05)the mRNA levels of Copper- and zinc-containing superoxide dismutase(CuZnSOD),Manganese-containing superoxide dismutase(MnSOD) and glutathione peroxidase 1(GPx1) in jejunum and CuZnSOD, MnSOD, GPx1, and Glutathione peroxidase 4(GPx4) in ileum. In addition, supplying a moderate amount of Trp in diet resulted in increased glutathione peroxidase(GSH-Px) activity and reduced malondialdehyde(MDA) content in 14d(P < 0.05). In addition, dietary Trp not only up-regulated the mRNA levels(P < 0.05), but also increased the protein expression level of manganese-containing superoxide dismutase(MnSOD) and glutathione peroxidase 4(GPx4) in the jejunum and ileum of weaned piglets(P < 0.05), respectively.Collectively, the results indicated that Trp supplementation could improve the serum antioxidant capacity and increase intestinal antioxidant enzyme gene expression in weaned piglets.(3) The results showed that supplying a moderate amount of Trp in diet significantly increased(P < 0.05) the content of free amino acids, TDO and IDO activity in liver and jejunum in 7d, respectively. What’s more, Trp supplementation could increased(P < 0.05) ATB0, +, 4F2 hc, ASCT2 and B0AT1 expression in jejunum.a moderate amount supplementation of Trp in diet could significantly increase(P < 0.05) the content of free amino acids and ATB0,+, 4F2 hc expression in jejunum. Above all, the results indicated that Trp supplementation could increase weaned piglets’ protein deposition and provide the necessary material of the body source to rapid growth and development.Conclusion: Supplying a moderate amount of Trp in the low protein diet canimprove the growth performance, antioxidant capacity and body protein deposition of the weaned piglets. The antioxidant effect of tryptophan can be realized by increasing the expression levels of the antioxidant enzyme gene mRNA in intestine.Tryptophan can increase protein deposition through expressing the amino acid transport carrier. However, the mechanism of the amino acid transport carrier is much more complicated and needs to be further discussed. |
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