This study aimed to determine the effect of urea-calcium sulphate mixture (U-cas) levels in high-quality feed block (HQFB) on ruminal digestibility, fermentation and gas kinetics in rumen fluid of swamp buffalo by using in vitro techniques. The treatments were seven levels of U-cas incorporated in HQFB at 0, 3, 6, 9, 12, 15 and 18% and the experimental design was a completely randomized design. Gas production rate constants for the insoluble fraction, potential extent of gas and cumulative gas were linearly increased with increasing levels of U-cas in HQFB. The in vitro dry matter digestibility, in vitro organic matter digestibility, true digestibility and microbial mass were altered by treatments and were greatest at 18% U-cas supplementation. Concentrations of propionate were linearly increased with increasing levels of U-cas and was highest with U-cas supplementation at 18%. The NH3 -N concentration was highest when urea was added in the HQFB while NH3 -N concentration tended to be reduced with increasing level of U-cas. The findings suggest supplementation of 18% U-cas in HQFB improves kinetics of gas production, rumen fermentation, digestibility and microbial mass as well as controlling the rate of N degradation in the rumen of swamp buffalo.
Keywords: feed block; in vitro gas production technique; ruminant; slow-release urea.
© 2014 Japanese Society of Animal Science.