Effects of replacement different levels and sources of methionine with betaine on jejunal morphology, duodenal mitochondrial respiration, and lipid peroxidation in heat-stressed broiler chickens

This study aimed to investigate the effects of replacement different levels and sources of methionine (Met) with betaine on jejunal morphology, duodenal mitochondrial respiration, and lipid peroxidation in heat-stressed broiler chickens. A total of 1,200 one-day-old Ross 308 broilers were randomly assigned to two similar poultry houses. The experiment was designed as a 2 (ambient temperatures) × 2 (Met sources) × 3 (Met levels) × 2 (betaine amounts) split-plot factorial arrangement. Basal diets (Low-Met) were formulated with DL-or L-Met to meet Ross 308 nutrient recommendations except for Met which was 30% lower than the recommendation. Met level in basal diets was increased to the recommendation and/or 30% more than recommendation (High-Met) by supplemental DL-or L-Met. Betaine was or was not partially substituted at a 30% equivalent level of supplemental DL- or L-Met. HS was induced by increasing ambient temperature to 32 °C for 6 h daily in one house from 10 to 42 d. The highest feed conversion ratio (FCR) was observed in Low-Met diets. Low-L-Met diets showed greatest FCR than Low-DL-Met diets groups. Breast muscle malondialdehyde (MDA) concentration was decreased by increasing dietary Met level under HS. Duodenal MDA concentration and complex (Cox) III activity was lower and higher in L-Met diets than DL-Met diets, respectively. Cox II activity was increased in High-Met diets, and also was improved by betaine replacement. Villus height (VH) and Villus surface (VS) was increased in L-Met diets compared to DL-Met diets. Generally, L-Met was more effective than DL-Met in jejunal morphology, reducing duodenal MDA, and increasing Cox III activity. Betaine had the potential to be a partial replacement for Met.HIGHLIGHTS L-Met was more efficient than DL-Met in duodenal malondialdehyde concentration and complex III activity. Heat stress reduced the growth performance of broilers through its negative effects on intestinal development and duodenal activity of respiratory chain complexes. Betaine could have a protective effect on mitochondrial function in the tissues of broiler chickens.