Effects of different amounts of Saccharomyces cerevisiae supplementation on apparent digestibility and faecal parameters in horses fed high-roughage and high-concentrate diets

• We studied the effect of live yeast in high-roughage and high-concentrate diets.
• We analysed nutrients digestibility, faecal microbial profile and faecal pH.
• The Saccharomyces cerevisiae used was not able to induce changes in the microbiota.
• Cellulolytic population and fibre digestion were not improved with yeast inclusion.
• The effect of Saccharomyces cerevisiae supplementation appears to be strain-dependent.

The aim of this study was to evaluate the influence of different amounts of Saccharomyces cerevisiae (SC) supplementation in high-roughage (HR) and high-concentrate (HC) diets on apparent total tract digestibility (ATTD), faecal microbial profile and faecal pH. Eight gelding miniature horses, about 36-months-old with an average weight of 113±12 kg were randomly assigned into a double 4×4 Latin Square. Two distinct experiments of 4 periods each were conducted with SC-supplementation of 0 (control), 10, 20 and 30 g (5×108 cfu/g), per animal per day. Experiment 1 used a HR diet (70% grass hay, 30% concentrate) and experiment 2 used a HC diet (30% grass hay, 70% concentrate). Each experimental period consisted of 23 days: 15 adaptation days, 5 days for data collection and a 3-day-wash-out interval between periods. Nutrient digestibility was evaluated by total faecal collection for each animal. The cellulolytic and lactic acid bacteria populations in faeces were calculated and faecal pH was measured. In the HR diet, S. cerevisiae supplementation was not associated with any changes in ATTD of nutrients, microbial profile in faeces and did not increase faecal pH values. In the HC diet, only the addition of 20 g SC reduced crude protein digestibility when compared with the control group and 30 g SC. For the other variables of digestibility the amounts of SC supplementation did not differ from control group. Furthermore, the microbial profile in faeces and faecal pH were not affected by S. cerevisiae supplementation. The present study showed that the S. cerevisiae strain used was not able to induce any changes in the equine hindgut and did not improve the fibrolytic activity with high-roughage and high-concentrate diets.