Four ruminally and duodenally cannulated Nellore steers were assigned to a 4 x 4 latin square to study the effects of feeding monensin (M) and different sources of fat on the ruminal population of ciliate protozoa and ruminal pH. The experimental diets contained (DM basis) 19% of sugar cane and were supplemented with M [control (CTRL)], M plus calcium salts of fatty acids (CSFA), M plus whole cottonseed (MWCS), or only WCS. Ruminal contents were sampled at 0, 2, 4, 6, and 8 hours post-feeding. In order to identify the ciliate protozoa a Sedgwick-Rafter count cell and an optic microscope with slide area of 0.4362 mm² were used. No significant differences in ruminal pH were observed among diets. Both cottonseed treatments (MWCS and WCS) reduced the ruminal population of the ciliate protozoa investigated, mainly the Entodinium, possibly because of the slow release of fat. Ruminal counts of Diplodinium, Epidinium, Eudiplodinium, and total protozoa were all affected by time post-feeding. Calcium salts of fatty acids seemed to be inert in the ruminal environment because no significant changes were observed in the protozoa counts. Moreover, feeding CRTL and MWCS diets to Nellore steers did not change the ruminal population of ciliate protozoa in this trial.
calcium salt of fatty acid; cattle; cottonseed; ionophores; protozoology
