Effect of different doses of sulfur on voluntary intake of low-quality elephant grass and estimates of ruminal protozoa populations in crossbred heifers

The experiment was carried out in the Experimental Field of Coronel Pacheco belonging to EMBRAPA Dairy Cattle, Minas Gerais. The effects of the doses of sulfur (ammonium sulfate, 0.15%, 0.31%, 0.46% and 0.92%S fresh matter/day) on the ruminal protozoa population was evaluated by utilizing four 7/8 Holstein x Zebu, heifers arranged in 4 x 4 Latin square. Low quality elephant grass (76.1% NDF in DM), chopped with correction of the CP content to 7% with urea plus a mineral mixture without sulfur given directly into the rumen. Samplings of the ruminal content were done, one hour after feeding. The estimate of the ruminal microbial populations was done by means of the direct microscopy. The results were transformed to decimal logarithm and evaluated statistically. There were no significant differences among the treatments for microorganisms. The 0.92%S treatment presented the least dry matter intake and, in addition, caused start of intoxication in two animals. According to those results, doses of 0.31% of sulfur added to the diet promoted the increase of the ruminal microorganism populations and hence a greater voluntary intake.