The aim of this study was to determine the effect of a yeast culture (Saccharomyces cerevisiae CNCM I – 1077) addition in the diet of dairy cows on their rumen fermentation. Animals received a diet consisting of good maize silage with a higher dry matter content (18 kg), 6 kg of lucerne haylage, 5 kg of pea – silage, 3 kg of ensiled high moisture crimped corn, 1 kg of meadow hay, rape-cake 1 kg, ­brewer’s grain silage 4 kg, and 8.0 kg feed mixture. The yeast culture was added to the mixture in the dose 2.8*1010 cfu / day and cow. The supplement of yeast culture showed a positive effect on ruminal VFA production by experimental group cows in comparison with control, higher production (P < 0.01) of acetic acid (58.50 ± 1.2583b vs. 51.833 ± 2.409a %), and lower production of propionic and butyric acid (24.667 ± 1.3744a vs. 28.833 ± 1.863b %). The average utilisation of ammonia was higher by cows in treated group (12.267 ± 0.754 mmol / L), but difference was not significant. The difference in number of protozoa of cows in the control and experimental groups was significant (P < 0.05) different (308.333 ± 24.390a vs. 342.333 ± 10.9341b ths /1 ml of rumen fluid).

In our experimental study we used the four most commonly grown (in the Czech Republic) sorghum and Sudan grass hybrids from USA (Nutri Honey, Latte, Honey Graze, Big Kahuna) and one hybrid from Germany (Bovital). The aim of the study was to compare these hybrids and to find out the influence of the growing season length on their nutrient composition and digestibility of organic matter. Samples were taken in the first cut, always in 14-day intervals. The crop was sown in early June, sampling started on July 19, 2010 and finished 8 weeks later on September 13, 2010.When assessing the influence of the growing season’s length the following values and development trends were discovered. Constant decreases over the testing period were recorded in nitrogen compounds – by 62 % (133.13 g), easily soluble sugars – 55. 5 % (40.06 g), organic matter digestibility 25.7 % (182.93 g) and NDF (neutro – detergent fibre) digestibility 31.5 % (73.2 g). Increasing trend, on the other hand, was recorded in fibre – by 30.4 % (99.2 g) and its individual components: lignin, NDF and ADF (acido – detergent fibre).In the second part of the experiment we were studying the differences in nutrient composition and organic matter digestibility between the individual hybrids. Honey Graze was recorded as having the highest average content of easily soluble sugars 57.53 ± 0.43 g, with lowest fibre content (272.13 ± 2.49 g), lowest ADF content (331.4 ± 2.88 g) and NDF content (440.4 ± 4.20 g) and lignin (77.47 ± 0.71 g). This hybrid also showed the best organic matter of (657.07 ± 5.28 g); however, no statistically conclusive differences (P < 0.05) in terms of organic matter digestibility were recorded between this hybrid and the other ones. The Bovital hybrid had the highest content of nitrogen compounds over the entire growing season (138.73 ± 0.94 g). Statistically highly conclusive difference (P < 0.01) in nitrogen compounds was found between this hybrid and all the other ones (except Big Kahuna). Upon all the indicators, the best rated sorghum and Sudan grass hybrid in terms of nutrient composition and organic matter digestibility was Honey Graze.