Effect of rumen-specific live yeast supplementation on in situ ruminal degradation of forages differing in nutritive quality

Abstract

Interest in alternative rumen fermentation modifiers has increased significantly since the ban of antibiotic growth promoters in 2006 by the European Union. The use of live yeast in ruminant feed is nothing new, but the mode of action has only recently been described. Inconsistent results in efficacy have sparked a new interest in the role of different feedstuffs on the effectiveness of the live yeast as rumen fermentation modifier. We investigated the effect of a live yeast supplement on in situ ruminal degradation of four different forages, each varying in quality within forage species. The experimental design was a crossover study using eight rumen cannulated Jersey cows all being fed a lucerne based total mixed ration (TMR). Four cows received a control diet with no live yeast supplemented, and the other four received the control diet supplemented with 0.5g grams live yeast per cow per day. The live yeast was supplemented directly into the rumen via the rumen cannula. The adaptation to each treatment was 21 days and the sampling period was 10 days thereafter. Four forages (Eragrostis hay, lucerne hay, kikuyu and rye grass pasture) with 3 qualities within each forage (Low, medium and high) were ruminally incubated for 12, 24 and 36h to measure in situ NDFom and dry matter disappearance. Rumen fermentation parameters were also measured. Live yeast supplementation did not affect the performance of the cows or any of the rumen fermentation patterns measured. Within forages the live yeast treatment did not affect ruminal NDFom disappearance in the high quality forage category. For lucerne hay the live yeast treatment appeared to increase in situ NDFom disappearance in the medium quality category, and also the overall average that included all qualities. For kikuyu and rye grass, the live yeast treatment decreased the in situ NDFom disappearance in the lower quality category as well as the overall average. For the Eragrostis curvula hay the live yeast treatment did not have any effect on in situ NDFom disappearance. Further research are needed to better understand the interaction between forage species, forage quality and the efficacy of live yeast under different dietary scenarios.