The aim of this experiment was to investigate the effect of different levels of betaine (Bet) inclusion in the diet on the intestinal health of growing rabbits under summer heat. A total of 100 weaned Qixing meat rabbits aged 35 d with body weight of 748.61 ± 38.59 g were randomly divided into 5 treatment groups: control group (basal diet) and Bet groups (basal diet + 0.75, 1.0, 1.5 or 2.0 g/kg Bet). The average daily temperature in the rabbitry during the experiment was 30.48 °C and the relative humidity was 69.44%. Dietary addition of Bet had no significant effect on growth performance and health status of growing rabbits (P > 0.05), but it increased ileal secretory immunoglobulin A content compared to the control under summer heat (P < 0.05). Addition of 0.75 g/kg Bet up-regulated jejunal IL-4, down-regulated ileal TNF-α expression (P < 0.05). The addition of 1.0 g/kg Bet increased the villi height (VH) in the jejunum (P < 0.05). Serum glucose levels were reduced, and the expression of SLC6A20 was up-regulated in jejunum and ileum of rabbits fed with 1.5 g/kg Bet (P < 0.05). When added at 2.0 g/kg, Bet reduced serum HSP70 content, increased jejunal VH, and up-regulated duodenal SLC7A6, SLC38A2, mTOR and 4EBP-2 expression (P < 0.05). Correlation analysis revealed that intestinal mTOR expression was significantly and positively correlated with SLC7A6, SLC38A2, SLC36A1 and IL-4 expression (P < 0.05). Dietary addition of Bet can up-regulate the expression of anti-inflammatory factors through the AAT/mTOR pathway, improve the intestinal immune function, alleviate intestinal damage in growing rabbits caused by summer heat, and improve intestinal health.

中文翻译：

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饮食中添加甜菜碱可通过 AAT/mTOR 途径减轻夏季高温期间生长兔的肠道损伤

本实验的目的是探讨日粮中添加不同水平的甜菜碱（Bet）对夏季高温下生长兔肠道健康的影响。35日龄断奶七星肉兔100只，体重748.61±38.59 g，随机分为5个治疗组：对照组（基础日粮）和贝特组（基础日粮+0.75、1.0、1.5或2.0 g/kg）赌注）。实验期间兔舍内日平均温度为30.48℃，相对湿度为69.44%。日粮中添加贝特对生长兔的生长性能和健康状况无显着影响（P > 0.05），但夏季炎热条件下，与对照相比，回肠分泌型免疫球蛋白A含量增加（P < 0.05）。添加 0.75 g/kg Bet 上调空肠 IL-4，下调回肠 TNF-α 表达（P < 0.05）。添加 1.0 g/kg Bet 增加了空肠绒毛高度 (VH) (P < 0.05)。饲喂1.5 g/kg Bet后，血清葡萄糖水平降低，空肠和回肠中SLC6A20表达上调（P < 0.05）。当添加 2.0 g/kg 时，Bet 降低血清 HSP70 含量，增加空肠 VH，上调十二指肠 SLC7A6、SLC38A2、mTOR 和 4EBP-2 表达 (P < 0.05)。相关分析显示，肠道mTOR表达量与SLC7A6、SLC38A2、SLC36A1、IL-4表达量呈显着正相关（P < 0.05）。日粮中添加Bet可通过AAT/mTOR通路上调抗炎因子的表达，提高肠道免疫功能，减轻生长兔夏季高温造成的肠道损伤，改善肠道健康。