Effect of legume (Phaseolus calcaratus) hay supplementation on rumen microorganisms, fermentation and nutrient digestibility in swamp buffalo

The objective of this research was to evaluate the effect of Phaseolus calcaratus hay (PCH) supplementation on the intake, digestibility, rumen fermentation, microbial population (bacteria, protozoa, and fungi) and methane production in swamp buffaloes fed on rice straw based diet. Four, 2.5 year old rumen fistulated male buffaloes were randomly assigned according to a 4 × 4 Latin square design. The treatments were level of PCH supplementation at 0, 300, 600 and 900 g DM/hd/d as supplements. The PCH contained 18.3% crude protein (CP) and 2.8% condensed tannins (CT). All buffaloes were fed with rice straw ad libitum while additional concentrate (12.6% CP) was fed at 0.3% body weight (BW). The study revealed that PCH supplementation had no effect on rumen temperature, pH, NH3-N and blood urea N. Volatile fatty acid (VFAs), especially those of propionic acid and acetic acid concentrations in the rumen were maximized (P < 0.05) at 600 g/hd/d feeding level. However, concentrations of each VFA and the acetate to propionate ratio did not differ among treatments. Bacterial, protozoal and fungal zoospore populations were maximized (P < 0.05) at the intermediate PCH feeding levels. Rumen methane gas production was decreased linearly (P < 0.05) with increasing level of PCH supplementation. N utilization in the buffaloes differed among treatments, with PCH supplementation linearly increasing N retention and efficiency of microbial N supply. Furthermore, PCH supplementation linearly increased (P < 0.05) in terms of total DM intake, apparent digestibility of CP and OM, while, DM, NDF and ADF digestibilities were not affected. Supplementation of PCH at 600 g/hd/d was beneficial in swamp buffaloes fed rice straw as a basal roughage, as it resulted in increased DM intake, reduced protozoal and methane gas production in the rumen, increased N retention as well as efficiency of rumen microbial CP synthesis.