Effects of dietary supplementation of pre-weaned lambs with live yeast on rumen fermentation, gut development, performance, and blood health indicators

Abstract

This study evaluated the effects of supplementing pre-weaned lambs with live yeast (Saccharomyces cerevisiae CNCM I-1077; 3 x 10^9 CFU/kg DM) on rumen fermentation, blood metabolites, gut development, and performance. Forty-six male lambs were randomly assigned to two treatments in a completely randomised design: a control group (CTL) fed a starter concentrate, and a yeast group (YST) receiving the same concentrate supplemented with live yeast. Both groups had ad libitum access to diets and barley straw from two weeks of age until weaning at eight weeks. Rumen fluid and blood samples were collected at 7 and 10 weeks to assess fermentation parameters and metabolites, and rumen tissue samples were collected at slaughter to evaluate papillae development. Rumen fermentative activity increased from 7 to 10 weeks, with higher concentrations of volatile fatty acids (VFA), lactate, and ammonia-N (p < 0.001). YST lambs showed higher rumen concentrations of protozoa (p = 0.007) and anaerobic fungi (p = 0.009), and a 56% increase in total VFA concentration pre-weaning and slightly enhanced concentrate intake. Blood metabolites remained within a physiological range, and YST lambs showed higher β-hydroxybutyrate (p < 0.001) and total protein (p = 0.054) than CTL lambs. Yeast also reduced parakeratosis scores (p < 0.001) and increased papillae width (p = 0.020). However, growth performance was not significantly affected. These results suggest that live yeast supplementation during the pre-weaning period supports microbial colonisation and rumen papillae development, facilitating a smoother transition from liquid to solid feeding and improved rumen function post-weaning.