Effects of different levels of yeast Saccharomyces cerevisiae on ruminal ecosystem and ciliate protozoa population in Ghizel sheep

The purpose of this study was to evaluate effects of yeast culture on rumen fermentation parameters, rumen protozoa biodiversity and generic distribution in Ghizel sheep. Sixteen rams (33.8±6.5) were used in a completely randomized design and treatments contained 0, 2.5, 5 and 7.5 g YSC (yeast Saccharomyces cerevisiae)/head/day. Rumen fluid samples were collected from all rams pre feeding and 2 h after morning feeding. Protozoa were counted using a Neubauer Improved Bright-Line counting cell. Ruminal pH, Methylen Blue Retention Time and Sedimentation and Floating Time also were evaluated. Data were analyzed in a completely randomized design with 4 replacements by SAS software and treatment means were compared by the Duncan test. Ruminal pH of YSC treated sheep were higher than control sheep (P<0.05), also sheep that received YSC, had lower (P<0.05) MBRT and SFT than control group. According to obtained data, total count of protozoa population in both sampling time showed an upward trend by increasing of YSC level. Also generic distribution of protozoa were affected by yeast addition in both sampling time (P<0.05). Entodinium genus was the most popular ciliate protozoa which identified and counted in the ruminal fluid. Number of total protozoa was higher in the 7.5 g YSC treatment. It was concluded that YSC was affected ruminal fermentation mechanism, so YSC had potential for ruminal ecosystem manipulating.