Effects of live yeast Saccharomyces cerevisiae on fermentation parameters and microbial populations of rumen, total tract digestibility of diet nutrients and on the in situ degradability of alfalfa hay in Iranian Chall sheep.

The effects of live yeast Saccharomyces cerevisiae (LYSC, strain Sc 47) on rumen fermentation and microbial populations, digestibility of nutrients, degradability of alfalfa hay and on the performances of sheep were investigated in two experiments. In both experiments, animals in treatment groups were received 0, 2.5, 5 and 7.5 g of LYSC per sheep per day and were defined as control, 2.5, 5.0 and 7.5 g LYSC treatment groups, respectively. In the first experiment, four fistulated Chall sheep (49 +/- 0.5 kg BW) were kept in individual metabolic crates under a 4x4 Latin square design and fed a Total Mixed Ration (TMR) containing of barely (48%), wheat bran (16%), shelled corn (5%), mineral-vitamin mix (1%) and of alfalfa hay (30%). In the second experiment, 28 sheep (48 +/- 0.5 kg BW) were assigned into four treatment groups under a complete randomized design and fed a TMR containing of barely (60%), wheat bran (7%), cottonseed meal (2%), mineral-vitamin mix (1%) and of alfalfa hay (15%) and wheat straw (15%). The highest and the lowest ruminal pH values (p < 0.01) were recorded for sheep in 2.5 g LYSC and control groups, respectively. At 3 h post-feeding, the total VFA of rumen fluid was increased (p < 0.01) from 91.26 to 103.34 mmol L(-1) in control vs. 2.5 g LYSC groups. The ruminal NH3-N of sheep was decreased (p < 0.01) from 159.63 to 128.90 mg L(-1) in control vs. 2.5 g LYSC groups. Bacterial populations of rumen fluids were differed from 14 to 43% in treatment groups although the differences were not significant. Compared to the other groups, voluntary feed intake was higher (p < 0.01) in 5.0 g LYSC group and this was ended to an inappropriate feed to gain ratio in this group. It can be concluded that the use of LYSC at a level of 2.5 g per sheep per day could improve the ruminal fermentation and resulted in a relatively better performances in Chall sheep.