The effects of betaine supplementation in diets containing different levels of crude protein and methionine on the growth performance, blood components, total tract nutrient digestibility, excreta noxious gas emission, and meat quality of the broiler chickens

The effects of betaine supplementation on growth performance, blood components, nutrient digestibility, excreta noxious gas emission, and meat quality of broiler chickens were examined using different dietary crude protein (CP) and methionine (Met) levels. A total of 768 Ross 308 broiler chickens were allotted to four treatments, with 12 replications of each treatment conducted over 6 wk. Treatments were factorially designed, with 2 levels of CP [Starter: CP 21% (low Met) and 23% (high Met); Finisher: CP 18% (low Met) and 20% (high Met)] and 2 levels of betaine supplementation (0 and 0.12%). Body weight gain and feed conversion improved significantly as dietary levels of protein increased (P < 0.05), but the results for betaine supplementation differed. The concentrations of serum total protein, albumin, and glutathione peroxidase (GPx) were elevated by either the supplementary betaine or the CP (P < 0.05). In addition, serum albumin concentration significantly increased in groups fed low CP amounts and betaine 0.12% compared with groups fed low CP only (P < 0.05). Total tract digestibility of nitrogen in broilers fed high CP amounts or 0.12% betaine, was observed to be greater than that in groups fed low CP amounts or no betaine treatment (P < 0.05). Supplemental betaine affected excreta ammonia gas emission, and hydrogen sulfide concentrations decreased significantly in low CP-fed groups (P < 0.05). Breast meat quality and relative organ weights were not influenced by CP levels or dietary betaine supplementation. These results suggest that betaine does not increase productivity, but may affect serum total protein, albumin, GPx, excreta ammonia emission, and nitrogen digestibility in broiler chickens. In addition, betaine supplementation is more effective in increasing serum albumin concentration when it was added in low CP (low Met) diets.