Manipulation of ruminal fermentation and methane production by supplementation of rain tree pod meal containing tannins and saponins in growing dairy steers

Abstract

Four rumen-fistulated dairy steers were used in a 2×2 factorial arrangement in a 4×4 Latin square design. The main factors were two roughage-to-concentrate ratios (R:C, 60:40 and 40:60) and two supplementation levels of rain tree pod meal (RPM) [0 or unsupplemented and 60g/kg of total dry matter (DM) intake]. Chopped 30g/kg of urea-treated rice straw was used as a roughage source. All animals received dietary according to respective R:C ratios at 25g/kg body weight. The RPM contained condensed tannins and crude saponins at 84 and 143g/kg of DM respectively. It was found that total volatile fatty acids (VFAs) and propionate concentrations were increased (p<0.01), while acetate concentration, acetate-to-propionate ratio, CH4 production and protozoal numbers were decreased (p<0.01) when steers were supplemented with RPM and 600g/kg of concentrate. Allantoin excretion was found different by both R:C ratio and supplementation of RPM, with the highest value at R:C of 40:60 with 60g/kg RPM (123.6mmol/day) (p<0.05). Allantoin absorption and microbial crude protein were increased (p<0.05) with an increasing concentrate ratio. Moreover, efficiency of microbial protein synthesis was increased (p<0.05) by feeding a higher ratio of concentrate (R:C 40:60) and supplementation of RPM. Based on this study, it is suggested that supplementation of RPM was beneficial for dairy cows fed on high roughage ratio, which could improved rumen fermentation by reducing fermentation gas loss, thus improving VFA profiles and thus enhancing efficiency of microbial protein synthesis.