Research Information System
Animal Feed Science and Technology, vol.331, 2026 (SCI-Expanded, Scopus)
Heat stress impairs growth, feed efficiency, and metabolic function in lambs. Rumen-protected betaine (RPB) may alleviate these effects by enhancing thermotolerance, improving nutrient utilization, and supporting rumen function. This study evaluated the effects of dietary RPB supplementation on growth performance, nutrient digestibility, rumen fermentation, nitrogen metabolism, microbial protein synthesis, and glucose tolerance in heat-stressed lambs. Forty crossbred lambs [Île-de-France × (Dalagh × Romanov)] with an initial body weight of 33.3 ± 2.67 kg were randomly assigned to four treatments: (i) control (CTRL, no RPB), (ii) RPBL (low dose of 2 g RPB/head/day), (iii) RPBM (medium dose of 4 g RPB/head/day), and (iv) RPBH (high dose of 6 g RPB/head/day) for 67 days. RPB supplementation improved final body weight, average daily gain, and feed conversion ratio (p < 0.01), without affecting dry matter intake (DMI). Apparent digestibility of crude protein and fiber fractions increased linearly (p < 0.05). Ruminal NH₃-N concentrations declined (p < 0.01), while total volatile fatty acids, acetate, and butyrate increased (p < 0.05). RPB also enhanced nitrogen retention, reduced urinary and fecal nitrogen excretion (p < 0.01), and increased microbial protein synthesis (p < 0.001). Furthermore, glucose tolerance tests revealed improved glucose clearance and reduced insulin responses in RPB-fed lambs (p < 0.001). In conclusion, RPB supplementation, particularly at medium levels, enhanced growth performance, nutrient digestibility, nitrogen utilization, rumen fermentation efficiency, and glucose metabolism in lambs under heat stress. These findings highlight RPB as a promising nutritional strategy to improve resilience and productivity in hot climates.