Effect of live yeast and yeast cell wall Saccharomyces cerevisiae diet supplementation on faeces chemical composition and growth performance in growing and finishing beef steers

The effect of live yeast (LY) and yeast cell wall (YCW) Saccharomyces cerevisiae diet supplementation were investigated in 30 Charolaise beef steers in the growing phase, 15 days after arrival in the farm, and in 30 Charolaise beef steers at the beginning of the finishing stage. Growing and finishing groups were randomly divided into three equal subgroups: supplemented with live cell yeast + yeast cell wall (GA) of Saccharomyces cerevisiae; supplemented with yeast cell wall (GB) of Saccharomyces cerevisiae (outer layer of yeast cell walls); and no supplement (growing control, GC); supplemented with live cell yeast (5 g/head) + yeast cell wall (15 g/head) (FA); supplemented with live cell yeast (5 g/head) (FB) based on Saccharomyces cerevisiae; and no supplement (finishing control, FC). Faeces samples were collected before (T0), after 21 (T1) and 42 (T2) days of the start of the study, which took place simultaneously and analysed for dry matter (DM), Ash, crude protein (CP), ethereal extract (EE), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) and Starch detection. Dietary supplementation of LY and YCW increased (P<0.05) DM, ADF and ADL faecal concentrations in the growing phase; DM, ADL and Starch faecal concentrations in the finishing phase. T2/FC Diet showed a significant effect (P<0.001) of different diets respect to T2/FB in the finishing stage. The obtained results suggest that yeast supplementation do not have beneficial effects with all type of diet condition. Further studies are needed to obtain more information on the mechanisms by which yeast stimulates nutrient digestibility and animal productivity in order to predict dietary conditions from which the benefits of yeast supplementation can be reasonably expected.