Degradability of grasses, ruminal fermentation and protozoa in beef cattle on diet with different additives

SUMMARY Four cattle rumen fistulae were fed on Latin Square with four treatments including the daily addition into rumen of: yeast (5g), monensin (200mg), Fator P (3g) and control. In situ degradability was determined with three tropical grasses: Tifton-85, Brachiaria, Mombasa and Mombasa silage, as well as ruminal pH, production of volatile fatty acids, ammonia-N and protozoa population. There was no significant interaction between treatment and grasses and significant differences between treatments, except in fraction b of Brachiaria and Mombasa silage. The Mombasa showed high solubility of DM and NDF compared to other grasses and Brachiaria higher solubility of CP. Processing of Mombasa as silage promoted reduction of soluble fraction and potential (PD) and effective degradabilities (ED) of DM and NDF and increased soluble fraction and ED of CP. Monensin produced lower production of acetic acid, higher of propionic and lower acetic: propionic acid. Yeast and Fator P showed higher total acids concentration than monensin and control. Diplodiniinae protozoa was increased with monensin compared to the control diet, but there was no difference in Entodinium and total ciliates between treatments. Tropical grasses in the form of hay and silage have different ruminal degradability not being influenced by additives in the diet, but these affect fermentation and protozoa population in the rumen.