This short-term study evaluated the effects of dietary betaine supplementation over 4 weeks on feed intake, milk production, nutrient digestibility, blood metabolites, and ruminal microbial communities in heat-stressed Holstein cows. Thirty lactating cows were randomly divided into a control group and a treatment group supplemented with 80 g/day of natural betaine extract for 4 weeks during summer. Betaine supplementation significantly increased dry matter intake (21.0 vs. 18.7 kg/day; p ≤ 0.05) and milk yield (35.4 vs. 31.2 kg/day; p ≤ 0.05) compared to the control. Milk composition, including fat and protein content, also improved (p ≤ 0.05). Cows receiving betaine had lower rectal temperatures (p = 0.02) and respiration rates (p = 0.01), indicating reduced heat stress. Serum concentrations of inflammatory markers-ceruloplasmin, haptoglobin, and serum amyloid A-were significantly lower in the betaine group by Week 4 (p ≤ 0.05). Plasma and rumen amino acid profiles, particularly lysine and methionine, were better preserved in the betaine group (p ≤ 0.05). Ruminal concentrations of volatile fatty acids increased (p ≤ 0.05), and the abundance of beneficial microbial species, such as Fibrobacter succinogenes, Butyrivibrio proteoclasticus, and Megasphaera elsdenii, was enhanced (p ≤ 0.05). These findings suggest that betaine supplementation is an effective nutritional strategy to improve dairy cow performance, reduce inflammation, and stabilise ruminal microbiota during heat stress.
Abdelmegeid et al. (Sun,) studied this question.