Effect of high altitude on nutrient digestibility, rumen fermentation and basal metabolism rate in Chinese Holstein cows on the Tibetan plateau

Abstract

Two experiments were conducted to investigate the effect of two altitudes (3600 and 1600 m) on nutrient digestibility, rumen fermentation and basal metabolism rate in Chinese Holstein cows. Experiment 1 was conducted to investigate the effect of high altitude (3600 m) on rumen fermentation, in vitro dry matter degradability, and nitrogen metabolism compared with low altitude (1600 m) in Chinese Holstein cows. Results indicated that total volatile fatty acids concentration, total gas production and gas coefficient a, b and c, efficiency of microbial protein synthesis and in vitro dry matter degradability were lower at 3600 m than 1600 m (P < 0.05). The number of protozoa and ammonia nitrogen concentration was higher at 3600 m than 1600 m (P < 0.05). We concluded that carbohydrate fermentation in the rumen was impaired, and ammonia nitrogen used for microbial nitrogen synthesis was also decreased at high altitude of 3600 m compared with 1600 m. Experiment 2 was conducted in vivo to investigate the effect of high altitude on apparent nutrient digestibility and basal metabolism rate in Chinese Holstein cows. Results indicated that the apparent digestibility of the diet’s dry matter, organic matter, neutral detergent fibre and acid detergent fibre was lower at 3600 m than those at 1600 m, respectively (P < 0.05). In Chinese Holstein cows, basal metabolism rate was increased with increasing level of altitude (P < 0.05). The results indicated that the high altitude of the Tibetan plateau impaired rumen fermentation and elevated the basal metabolism rate of Chinese Holstein cows.