Betaine addition to dietary can alleviate intestinal injury to growing meat rabbits in summer heat through the AAT/mTOR pathway

Abstract

Background 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 meat rabbits under summer heat. A total of 100 weaned Qixing meat rabbits aged 35 days with similar body weight (748.61 ± 38.59 g) were randomly divided into five 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%. Results Dietary addition of Bet had no significant effect on growth performance and health status of growing meat rabbits (P > 0.05), but it increased ileal secretory immunoglobulin A (sIgA) 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 in rabbits, and up-regulated jejunal and ileal SLC6A20 expression fed with 1.5 g/kg Bet (P < 0.05). When added at 2.0 g/kg, Bet reduced serum HSP70 content, jejunal VH was increased, 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). Conclusions 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 meat rabbits caused by summer heat, and improve intestinal health, with the best results achieved when the amount of Bet was 2.0 g/kg.