Meta-analysis of effects of concentrate supplementation in warm and cold seasons on growth performance and rumen fermentation of grazing yaks

The yak (Bos mutus) is a key economic livestock species in the Qinghai-Tibet Plateau. Its nutrition and production efficiency are directly affected by the seasonal fluctuations in forage resources. Concentrate supplementation serves as a key strategy to alleviate nutritional imbalance in grazing yaks during cold and warm seasons; however, the scientific validity and applicability still require further validation. The study objective was to evaluate the effects of concentrate supplementation in warm and cold seasons on growth performance and rumen fermentation of grazing yaks using meta-analysis based on existing literature data. Through literature search and screening, 19 studies concerning grazing yaks meeting screening criteria were finally included for subsequent analysis. The results showed that concentrate supplementation in both cold and warm seasons significantly improved the growth performance of grazing yaks (P = 0.001), and the effect was better in the cold season. Subgroup analysis showed that young yaks (18–30 months old) had the best average daily gain (ADG) improvement in both cold and warm seasons (P = 0.001). The yaks of the concentrate supplemental level > 2 kg·(head·d)⁻¹ group comprised the most significant ADG increment in the cold season (P = 0.014), and yaks of the ad libitum feeding group exhibited the most significant increase in ADG in the warm season (P = 0.001). The concentration of ammonia nitrogen (NH₃-N), total volatile fatty acid (TVFA), and molar proportion of propionate and butyrate in the rumen were significantly enhanced (P = 0.001), and the pH (P = 0.016) and molar percentage of acetate in the rumen were significantly decreased (P = 0.013). We statistically confirmed that concentrate supplementation can improve growth performance and optimize rumen fermentation of yaks and provide data support for precise supplemental feeding and feeding management of grazing yaks.