LAUSR

BACKGROUND The objectives of this study were to investigate the effects of taurine on rumen fermentation, rumen bacterial community and metabolomics, nitrogen metabolism and plasma biochemical parameters in beef steers. Six castrated Simmental steers (liveweight with 402 ± 34 kg) and three levels of taurine, i.e. 0, 20, 40 g d-1 were assigned in a replicated 3 × 3 Latin square design. Each experimental period included 15 days for adaptation and 5 days for sampling. RESULTS Supplementing taurine did not affect the ruminal pH and concentrations of ammonia nitrogen and volatile fatty acids (P > 0.10), but linearly increased the ruminal concentrations of taurine (P < 0.001) and microbial crude protein (P = 0.041). Supplementing taurine linearly increased the neutral detergent fiber digestibility (P = 0.018), and tended to linearly increase dry matter (P = 0.095), tended to increase the fecal nitrogen (P = 0.065), and increased the urinary taurine excretion (P < 0.001). Supplementing taurine quadratically increased the plasma concentration of triglycerides (P = 0.017), tended to linearly decrease growth hormone (P = 0.074), but did not affect other plasma parameters (P > 0.10). Supplementing taurine modified the rumen bacterial community and increased the ruminal concentration of taurine metabolite 2-hydroxyethoxy sulfonic acid (P < 0.001). CONCLUSION It was concluded that taurine improved ruminal microbial crude protein synthesis and increased fiber digestibility and through modifying rumen bacterial community. It is necessary to clarify the ruminal hydrolysis of taurine in steers. This article is protected by copyright. All rights reserved.