Urea Utilization by Cattle as Influenced by Casein
THE influence of casein on urea-nitrogen utilization by cattle was investigated in two studies. In a fattening study, the inclusion of casein to a soybean meal (SBM) or urea-supplemented ration depressed both average daily gain (ADG) and average daily feed intake (P<.05}. Casein addition, on the other hand, significantly (P <.05 increased rumen :ammonia concentration. The second and metabolism study involved the use of identical rations as in the fattening study. Cattle fed rations with casein did not show any significant decrease in nitrogen retention as compared to cattle fed rations without casein. However, there was a non-significant drop in nitrogen retention, and an increase in urinary nitrogen excretion attributable to casein. Ruminal histamine observed for steers on the fattening study was higher than that noted for steers on the metabolism study. Part of the poor performance of steers on the casein diets could be attributed to the higher urinary nitrogen excreted and the elevated ruminal histamine levels observed.