EN
The aim of this experiment was to study the influence of substituting soybean meal (SBM) with post-fermentative yeast biomass (post-FYeB) powder on feed intake, ruminal fermentation, and bacteria and protozoa content in rumen fluid in beef cattle. The study was conducted on four male Thai native beef cattle at around 1 to 2 years of age with an initial body weight (BW) of 120 ± 20 kg. The experimental design was a 4 × 4 Latin square design and the dietary treatments included four levels of SBM substitution with post-FYeB in concentrate feed: 0, 33, 67 and 100%. The used post-FYeB contained 26.4% crude protein. Increasing levels of post-FYeB in concentrate diets did not alter roughage intake and total intake (P > 0.05). Rice straw intake ranged from 2.0 to 2.1 kg DM/day while total intake ranged from 2.7 to 2.8 kg DM/day. Ruminal pH and temperature in cattle fed various levels of post-FYeB were not significantly different among treatments. Total volatile fatty acids (VFA) and VFA profiles were not altered by different levels of post-FYeB. Post-FYeB addition into diet did not change bacteria and protozoal populations (P > 0.05). Thus, the inclusion of postFYeB as a replacement of SBM in ruminant diets up to 100% is suggested.