The objective of this research was to evaluate the effect of feeding fresh cassava root (CR) along with a feed block containing high was to sulfur (FBS) on feed intake, digestibility, rumen fermentation, and blood thiocyanate concentration in Thai native beef cattle. Four Thai male native beef cattle, initial body weight (BW) of 130 + 20.0 kg, were used in this study. The experiments were randomly assigned according to a 2 × 2 factorial arrangement in a 4 × 4 Latin square design. The main factors were supplemented fresh CR levels (1.0 and 1.5% BW) and across to a feed block supplemented with sulfur added 2% (FBS-2) and 4% (FBS-4). Intakes of rice straw, concentrate diets, and FBS were not affected by treatments. Intakes of CR, sulfur, and total intake were significantly altered by the FBS treatment. The apparent dry matter and organic matter digestibility coefficient were significantly higher in animals fed FBS-4 than in those fed FBS-2. The ruminal ammonia nitrogen concentration was not affected by treatment and ranged from 15.6 to 17.6 mg/dl. Populations of protozoa and fungal zoospores were similar across treatments, whereas the bacterial population was significantly different between sulfur levels in the feed block. Feeding CR with FBS did not change total volatile fatty acid (VFA) concentrations and VFA profiles except for the propionic acid concentration, which was higher in the group with CR supplementation at 1.5% BW. Cattle fed CR with FBS showed similar blood urea nitrogen concentration at various feeding times and overall. In contrast, CR supplementation at 1.5% BW with FBS-2 increased blood thiocyanate concentrations. Therefore, supplementation of FBS-2 was beneficial to Thai native beef cattle fed with 1.5% BW fresh CR as it improved digestibility and rumen fermentation presumed, because HCN from fresh cassava root was converted into thiocyanate, which is nontoxic to farm animals.
Keywords: Cattle; Feed block; Fresh cassava root; Sulfur; Thiocyanate.