Dietary dimethylglycine sodium salt improves growth performance, liver function, and meat quality of broilers exposed to heat stress.

Heat stress is a major environmental challenge that impairs growth performance, hepatic redox homeostasis, and meat quality in broilers, primarily through oxidative stress and mitochondrial dysfunction. Dimethylglycine sodium salt (DMG-Na), a methyl donor involved in one-carbon metabolism, is known to regulate redox balance and mitochondrial function, indicating its potential to alleviate heat stress-induced physiological disturbances. This study evaluated the protective effects of dietary DMG-Na on heat stress-induced physiological and metabolic disturbances in broilers. Eight hundred 21-day-old chicks were randomly assigned to a thermoneutral control group (TN) or heat stress groups receiving a basal diet supplemented with 0, 200, 400, or 600 mg/kg DMG-Na (HS, HSD2, HSD4, HSD6). Heat stress significantly reduced average daily gain and feed intake, increased feed conversion ratio, elevated serum ALT and AST activities, disrupted redox balance, impaired mitochondrial antioxidant capacity and energy metabolism, and deteriorated meat quality (P < 0.05). Dietary DMG-Na supplementation markedly alleviated these adverse effects by improving growth performance, enhancing antioxidant enzyme activities, reducing oxidative damage, restoring mitochondrial respiratory chain function and ATP production, and improving meat quality parameters (P < 0.05). Transcriptomic and quantitative gene expression analyses further demonstrated that DMG-Na partially reversed heat stress-induced alterations in genes related to redox regulation, cell adhesion, and mitochondrial function. Overall, these findings indicate that dietary DMG-Na supplementation effectively mitigates heat stress-induced oxidative and metabolic disturbances in broilers, with 200 mg/kg appearing sufficient to achieve most protective effects, suggesting a plateau response at higher inclusion levels.