Effect of feeding hydrolyzed and live yeast (Saccharomyces cerevisiae) on ruminal fermentation, blood biochemical characteristics and performance of Holstein lactating cows under heat stress

Abstract

Introduction: This study was conducted to evaluate and compare the effects of feeding live
and hydrolysed yeast to Holstein lactating cows under heat stress on ruminal fermentation,
biochemical blood metabolites, milk production and composition.
Materials & methods: Cows (n=15) were randomly divided into three groups and five
replicates and housed in a region with tropical condition. Cows received basal diet with or
without live yeast or hydrolysed yeast. Control group received basal diet; other groups
received 1.0 g/day/head live yeast and 20 g/day/head hydrolysed yeast. The amount of milk
production and milk composition, rumen fermentation parameters and blood biochemical
parameters were analyzed.
Results: Live yeast supplementation resulted in higher dry matter intake compared with
hydrolysed yeast and the control. The apparent digestibility of nutrients was not differed
among treatments, except fiber. Fiber digestion improved in cows fed diet supplemented
with live yeast. Live yeast supplementation increased acetate and acetate to propionate ratio
and decreased propionate level, but hydrolysed yeast had no significant effect. Average milk
production was the highest in cows received live yeast. No difference was found for milk
compositions and its fatty acid profiles.
Conclusion: It was concluded that 1.0 g/d/head live yeast could, but hydrolysed yeast could
not, improve feed consumption and milk production in dairy cows during the hot season.