Effects of Bismuth Subsalicylate and Calcium-Ammonium Nitrate on Ruminal Fermentation of Beef Cattle

A duplicated 5×5 Latin square design was used to determine the effects of bismuth subsalicylate (BSS) and encapsulated calcium-ammonium nitrate (eCAN) on ruminal fermentation of beef cattle consuming bahiagrass hay (Paspalum notatum) and cane molasses. Ten ruminally cannulated beef cattle were randomly assigned to 1 of 5 treatments as follows: 3.3 g/kg of BW of molasses (CTRL); CTRL + 182 mg/kg of BW of urea (N0B0); CTRL + 538 mg/kg of BW of eCAN (N1B0); N0B0 + 58.4 mg/kg of BW of BSS (N0B1); and N1B0 + 58.4 mg/kg of BW of BSS (N1B1). With exception of CTRL, all treatments were isonitrogenous. Ruminal fluid and rectal temperature was collected 4× per d for 3 d to determine ruminal changes every 2 h from 0 to 22 h post feeding. Ruminal gas cap samples were collected at 0, 3, 6, 9, and 12 h on d 0 of each period followed by 0 h on d 1, 2, 3, and 14. Repeated measures data were analyzed using the MIXED procedure of SAS with the fixed effects of treatment, time, treatment × time, square, period, and animal within square, and the random effect of animal within treatment. For non-repeated data, the model included the fixed effects of treatment, square, period, and animal within square. Orthogonal contrasts were used to evaluate the effects of NPN, eCAN, BSS, and eCAN × BSS. There was no treatment effect (P > 0.05) on concentrations of H₂S on d 0, 1, 2, or 14; however, on d 3, concentrations of H₂S were reduced (P = 0.018) when NPN was provided. No effect of treatment (P = 0.864) occurred for ruminal pH. There was an effect of eCAN on total concentrations of VFA (P = 0.011), where a 6% reduction occurred when eCAN was provided. There were effects of NPN (P = 0.001) and eCAN (P = 0.009) on concentrations of NH₃-N, where cattle consuming NPN had lesser concentrations than those consuming eCAN compared to urea. Total concentrations of VFA and NH₃-N were not affected (P > 0.05) by BSS. There was an effect of BSS (P = 0.009) on rectal temperature, where cattle not consuming BSS had greater temperatures than those receiving BSS. In conclusion, eCAN does not appear to deliver equivalent ruminal fermentation parameters compared to urea, as indicated by reductions in total concentrations of VFA and NH₃-N.