[Comparative studies of the digestibility of wheat straw pellets with different proportions of concentrated feed in sheep and bulls. 2. Rumen fermentation studies].

4 sheep (wethers) and 4 bulls (130-140 kg live weight) received pellets of straw and concentrated feed of the charges 1-5 produced from the same wheat straw. The quota of wheat coarse meal in the pellets was, in the sequence 1 to 5:31.4; 29.7; 15.3; 11.5 and 7.8% (charge 5 contained in addition to this 7.4% dried sugar beet). The crude fibre content in the DM, in the same sequence, was as follows: 25.9; 28.1; 28.7; 31.7 and 34.4%. The total content of volatile fatty acids (VFA) in the rumen fluid of the sheep was between 96.6 and 97.8 mmol/l (all 5 charges) and in the rumen fluid of the bulls between 83.4 and 90.5 m mol/l. There were no significant differences between the groups. The molar acetic acid content after the feeding of charge 1 (poorer in crude fibre) was 67.4% (sheep) and 68.0% (bulls) and rose with the increasing crude fibre content in the case of charge 5 to 70.5% and 72.2% resp. The content of propionic acid did not rise in the pelleted rations with the growing cereal quota and, identically for sheep and bulls, amounted to 17.7 mol% and 17.8 mol% on an average of the 5 rations. The molar butyric acid content decreased significantly with both species with the growing crude fibre content of the pelleted charges. The sum of the VFA with branched chains (isobutyric acid, valeric acid and isovaleric acid) increased significantly in both species with the growing quota of cereal coarse meal in the pellet charges. In the bulls, however, the increase was distinctly steeper, which is probably connected with the significantly higher pH-value and a higher proteolysis rate in the rumen fluid of the bulls (charges 1 to 2) in comparison with the sheep.