Life yeast is known to improve rumen fermentation characteristics and performance, especially with high concentrate diet, while reports on inactivated yeast are ambiguous. Therefore, the present study focused on short-term effects of inactivated yeast (Levabon®) with an inclusion rate of 0 or 50 g per head per day on in situ rumen dry matter degradability (ISDMD) of a total mixed ration (66.6% grass silage, 14.5% maize silage, 6.3% soybean meal, 6.3% wheat and 6.3% barley) and its individual feedstuffs at low level of feed intake (7 kg/day) and at low concentrate diet. Eight non lactating rumen fistulated dairy cattle were used in a 4 × 2 Latin square designs in two identical periods (each period extended for 23 days) to measure in situ rumen degradation characteristics. Samples from the ruminal fluid were collected for further investigation (ruminal pH value, volatile fatty acids (VFAs), and ammonia nitrogen as well as acetate propionate ratio). The obtained results of this experiment indicated that Levabon® had no effect on rumen dry matter degradability of the total mixed ration and its individual feedstuffs. Levabon® had no effect on rumen dry matter degradability parameters and effective rumen dry matter degradability of the different feedstuffs. Moreover, rumen physiological parameters (rumen pH values, volatile fatty acid (VFAs) and ammonia nitrogen, as well as acetate propionate ratio), was not affected due to the addition of Levabon®. In conclusion, under the present feeding conditions (low level of feed intake and high proportion of structured roughage), Levabon® had no effect on rumen dry matter degradability or rumen physiological parameter due to absence of dietary factors challenging rumen fermentation.
Key words: Levabon®, rumen manipulation, rumen fermentation, in situ method, ammonia, volatile fatty acids.