Effects of Glutamine on Rumen Digestive Enzymes and the Barrier Function of the Ruminal Epithelium in Hu Lambs Fed a High-Concentrate Finishing Diet

SIMPLE SUMMARY: It has been reported that goats fed a high-concentrate finishing diet had increased the short-chain fatty acid production and concentration; a decreased mean ruminal pH, leading to an increase in the epithelium’s permeability; destruction of the tight junctions between cells; and damage to the barrier function. Glutamine, as a conditionally nonessential amino acid, can maintain the acid base balance of body fluids, promote nitrogen balance, and strengthen the mucosa and the integrity of the tight junction proteins. In this study, we aimed to investigate if Gln (Glutamine) would improve the digestive enzymes’ activity, the ruminal epithelial barrier and fermentation, and immune responses by supplying energy to the mononuclear cells, improving the ruminal epithelium’s morphology and integrity, and mediating the mRNA expression of cytokines and tight junction proteins. ABSTRACT: The present experiment aimed to research the effects of glutamine (Gln) on the digestive and barrier function of the ruminal epithelium in Hu lambs fed a high-concentrate finishing diet containing some soybean meal and cottonseed meal. Thirty healthy 3-month-old male Hu lambs were randomly divided into three treatments. Lambs were fed a high-concentrate diet and supplemented with 0, 0.5, and 1% Gln on diet for 60 days. The experimental results show that the Gln treatment group had lower pepsin and cellulase enzyme activity, propionate acid concentration, and IL-6, TNF-α, claudin-1, and ZO-1 mRNA expression in the ruminal epithelium (p < 0.05); as well as increases in lipase enzyme activity, the ratio of propionic acid to acetic acid, the IL-10 content in the plasma, and the mRNA expression of IL-2 and IL-10 in the ruminal epithelium, in contrast to the CON (control group) treatment (p < 0.05). Taken together, the findings of this present study support the addition of Gln to improve digestive enzyme activity, the ruminal epithelium’s barrier, and fermentation and immune function by supplying energy to the mononuclear cells, improving the ruminal epithelium’s morphology and integrity, and mediating the mRNA expression of tight junction proteins (TJs) and cytokines.