Improving effects of dietary rumen protected γ‐aminobutyric acid additive on apparent nutrient digestibility, growth performance and health status in heat‐stressed beef cattle

This study was aimed to investigate the effects of rumen-protected γ-aminobutyric acid (RP-GABA) on apparent nutrient digestibility, growth performance and health status in heat stressed beef cattle. Fifty Jinjiang Yellow cattle were randomly assigned to 5 treatments (10 animals/treatment). Treatments 1 to 5 were basal diets affixed with 0 (control), 8, 16, 24 and 32 mg of RP-GABA/kg of body weight (BW) respectively. The trial lasted 45 days. Apparent digestibility of crude protein (CP), crude fiber (CF) and calcium (Ca) quadratically increased with increasing RP-GABA (p < .01), while apparent digestibility of phosphorus (P) tended to quadratically increase (p = .09). Dietary supplementation with increasing RP-GABA linearly increased DM digestibility and average daily gain (ADG) (p < .01), whereas the feed to gain (F:G) ratio linearly decreased with increasing RP-GABA (p < .01). The average daily feed intake (ADFI) value tended to linearly increase with RP-GABA supplementation (p = .08). Total protein (TP), blood urea nitrogen (BUN) and malondialdehyde (MDA) levels quadratically decreased (p < .01) with increasing RP-GABA, however albumin (ALB), glucose (GLU), superoxide dismutase (SOD), triiodothyronine (T3) and thyroxine (T4) levels quadratically increased (p ≤ .01). In conclusion, the present results indicated that dietary supplementation with RP-GABA led to improved nutrient digestibility, growth performance and antioxidant status in heat stressed beef cattle.