The aim of this work was to evaluate the influence of yeast (Saccharomyces cerevisiae)-fermented cassava bioethanol waste (YECAW) on feed utilization, ruminal fermentation, and microbial population in dairy calves fed a concentrate diet at 1% body weight (BW). Four male Holstein Friesian crossbred calves with an initial BW of 109 ± 6.23 kg were used in this research. The experimental design was a 4 × 4 Latin squared design and the dietary treatments were four levels of YECAW supplementation at 0%, 5%, 10%, and 20% concentrate mixture. The YECAW product contained CP at 25.1% dry matter (DM) and NDF and ADF at 65.2 and 40.6% DM, respectively. Inclusion of YECAW did not alter feed intake of rice straw, total intake, nutrient intake, and digestion coefficients (P > 0.05). Ruminal pH and temperature, ruminal ammonia-nitrogen, and blood urea-nitrogen (BUN) were not significant by YECAW levels supplementation (P > 0.05). Increasing YECAW levels did not adversely affect the population of bacteria, protozoa, and fungi and values ranged from 6.5 to 7.0 × 1012, 3.2 to 4.0 × 105, and 6.9 to 7.4 × 103 cells/ml, respectively (P > 0.05). Feeding of YECAW to dairy calves did not affect the total VFA, acetic acid (C2), propionic acid (C3), or butyric acid (C4) proportion (P > 0.05) which ranged from 102.6 to104.6 mmol/l, 70.7 to 72.0, 17.8 to 20.2, and 9.1 to 10.3 mol/ 100 mol, respectively. Therefore, feeding of YECAW is recommended because no adversely affect the utilization of feed and rumen characteristics and might be alternative protein source for ruminants.
Keywords: Cassava waste; Feed intake; Rumen fermentation; Ruminal microorganism; Ruminant.