Live yeast culture and monensin in high grain diets for cattle: rumen fermentation and “in situ” degradability

Abstract

Live yeast cultures have been used as an alternative to replace antibiotics in diets for ruminants. Therefore, the aim was to evaluate the effects of adding live yeast culture (Saccharomyces cerevisiae, Beef Sacc®, Alltech, Inc.), monensin (Rumensin®, Elanco, Inc.) and the combination of both additives in high grain diets, on rumen fermentation patterns, protozoa organisms and in situ degradability of diet components. Four rumen-cannulated steers were fed a basal ration (2.8Mcal ME/kg DM, 14% CP) and submitted to one of four treatments following a 4x4 Latin Square design: control (CON, no additives), yeast (YEA, 0.6g/kg of dry matter), monensin (MON, 0.3g/kg of dry matter) and monensin plus yeast (MON+YEA). After 14 days of diet adaptation, the rumen fermentation parameters, the protozoa numbers and the degradation kinetics of corn (CO), soybean meal (SM) and soybean hulls (SH) were assessed. Feed additives did not affect rumen pH, butirate and ammonia nitrogen concentrations, but decreased total short chain fatty acids (mM). MON and MON+ YEA decreased acetate (%) and acetate:propionate ratio whereas propionate was increased by MON and MON+YEA at all sampling times, and by YEA at 4 and 6h post-feeding only. YEA increased the number of protozoa whereas MON and MON+YEA inhibited those microorganisms (total organisms [x104/mL]). There were no effects of YEA and MON+YEA on in situ degradability parameters of any evaluated feed, however, MON increased NDF degradation rate of SH. Monensin effects on rumen fermentation are more significant than those observed when feeding live yeast cultures, and the combination of both additives does not improve their effects.