Effect of increased levels of urea in the diet on ruminal protozoal counts in four ruminant species.

Abstract

Summary Fistulated sheep, goats, cattle and buffaloe's were used to study the effect of substituting urea for 0, 36, 55 or 100% of cottonseed cake protein on the total counts, pool size and composition of protozoal population in the rumen. Highest protozoal counts were obtained on the 0 and the 100% urea-N diets and the lowest protozoal counts were observed in 55% urea-N diet. Sheep and goats had higher protozoal counts than buffalo and cattle. Protozoal pool size in the rumen of sheep was greater than of goats and that of buffalo was greater than for cattle. Increasing urea-N in the diet decreased growth rate of protozoa in vitro. The growth rate of protozoa in vitro was affected by postprandial time, but not by animal species. A mixture of Entodinia, Isotricba, Diplodinium and Polyplastron species was found in the rumen contents of all animal species. Entodinia sp. were predominant in all animals on the four diets. Increasing urea-N in the diet increased the percentage of Entodinia and reduced the other species so that negligible numbers of Isotricba, Diplodinium and Polyplastron were observed in 100% urea-N diet. Increased levels of urea increased the generation time (hr) of protozoa in sheep, goats, cattle and buffaloes.