Effects of energy and protein restriction on digestion and absorption in the gastrointestinal tract of Liuyang Black kids

The effects of key nutrient restriction on digestion and absorption in the gastrointestinal tract were investigated in 60 weaned Liuyang Black kids. Weaned kids in this study received one of the following diets (15 kids per treatment): diet with adequate nutrient supply (control diet), energy restriction diet (ER diet), protein restriction diet (PR diet), or both energy and protein restriction diet (EPR diet). The experiment included an adaptation period (0–6 d), a nutritional restriction period (7–48 d), and a recovery period in which all kids received a unified and normal diet (49–111 d). On d 48 and 111, 3 kids from each diet group were anaesthetised to collect samples of digesta, pancreas, and epithelia of the rumen and jejunum. When compared with control diet, the PR diet decreased the activity of exo-1,4-β-glucanase in the rumen and the amounts of Val and Phe transported from the jejunum mucosal side to the serosal side (p < 0.05). The ER, PR, and EPR diets decreased the activities of trypsin and α-amylase in the jejunum (p < 0.05). The EPR diet decreased the activities of exo-1,4-β-glucanase in the rumen, α-amylase in the pancreas, and the amounts of Val, Leu, Phe, and Arg transported from the jejunum mucosal side to the serosal side (p < 0.05). After 9 wk of nutritional recovery, the amount of Val transported from the jejunum mucosal side to the serosal side of kids in EPR group was still lower than that of kids in control group (p < 0.05), indicating prolonged effects even after nutritionally recovery. This study demonstrated that 6 wk of PR or EPR reduced the digestive and absorptive ability of the rumen and jejunum of weaned kids and the reduced absorptive ability was not fully recovered after 9 wk of nutritional recovery.