Effect of feeding feed blocks containing different levels of urea calcium sulphate mixture on feed intake, digestibility and rumen fermentation in Thai native beef cattle fed on rice straw

Four Thai native beef cattle were randomly assigned according to a 4 × 4 Latin square design to evaluate the effect of urea calcium sulphate mixture (U-cas) levels in feed block on feed intake, apparent digestibility of nutrients and rumen fermentation fed on rice straw based diet. The four dietary treatments were different levels of U-cas supplementation in feed block at 0, 120, 150 and 180 g/kg dry matter (DM), respectively. The present results revealed that rice straw intake increased with the increasing levels of U-cas inclusion in the feed block. The highest total intakes of DM and energy (ME, MJ/d) were in cattle receiving feed block containing U-cas at 180 g/kg DM, and followed by 150, 120 and 0 g/kg DM, respectively. Apparent digestibility of nutrients enhanced the increasing levels of U-cas supplementation in feed blocks, except acid detergent fiber. Rumen pH and temperature were not affected by U-cas levels inclusion in feed block. At 4 h post feeding, the concentration of ruminal ammonia nitrogen decreased with increasing levels of U-cas in feed blocks (P<0.05). Inclusion of U-cas at 180 g/kg DM in the feed block increased the ruminal propionic acid concentration at 4 h post feeding while ratio of acetic: propionic acid and acetic plus butyric: propionic acid were lower than those in other groups (P<0.05). Inclusion of U-cas at 180 g/kg DM as a slow release urea source in the feed block resulted in improving feeding value of the diets as rice straw base in Thai native beef cattle.