El Hassan, S. M., Newbold, C. J., Edwards, I. E., Topps, J. H., Wallace, R. J. (1996). Effect of yeast culture on rumen fermentation, microbial protein flow from the rumen and live-weight gain in bulls given high cereal diets. Animal Science, 62 (1), 43-48.Four groups each of eight Limousin X Friesian bulls, average weight 344 kg, were offered individually ad libitum diets comprising: 920 g rolled barley, 50 g cane molasses, 15 g urea and 15 g minerals/vitamins mix per kg or 867 . 5 g rolled barley, 50 g cane molasses, 7 . 5 g urea, 60 g soya-bean meal and 15 g minerals/vitamins mix per kg, plus or minus yeast culture (YC, 1 . 5 kg/t) (all weights fresh weights), until slaughter (460 kg). Rumen samples were obtained by stomach tube. YC decreased rumen ammonia concentrations (116 . 7, 56 . 0, 74 . 3, 45 . 7 (s.e.d. 19 . 40) mg/l for barley/urea, barley/urea/YC, barley/soya-bean meal and barley/soya-bean meal/YC, respectively). This was associated with increases (P <0 . 05) in both the total number of bacteria (2 . 3, 4 . 2, 3 . 5, 6 . 8 (s.e.d. 1 . 06) X 10(9) per ml, respectively) and the protein content of rumen fluid (7 . 7, 9 . 6, 8 . 7, 9 . 0 (s.e.d. 0 . 59) g/l, respectively). However, the flow of microbial protein from the rumen as estimated from the appearance of purine derivatives in the urine was unaffected (131, 130, 129, 147 (s.e.d. 12 . 6) g N per day, respectively). Thus although the animals responded to the undegradable rumen protein supplied by the soya-bean meal there was no significant response in live-weight gain with YC (1 . 28, 1 . 31, 1 . 42, 1 . 48 (s.e.d. 0 . 081) kg/day, respectively).Peer reviewe

Goats that had been inoculated with the causal organism of contagious caprine pleuropneumonia and treated, within a few days, with oxytetracycline or tylosin, were less severely affected than infected, untreated control goats. However, 20% of treated cases remained infective and were, presumably, capable of transmitting the infection.

Clinical cases of both Zn and Cu deficiencies are reported in a cattle farm in Kordofan Region of the Sudan after drought. The animals showed general weakness, stunted growth, infertility, parakeratosis and achromotrichia. There was macrocytic hypochromic anaemia and low Cu and Zn concentrations in sera. The condition was more prevalent in zebu-Friesian crosses than the local breeds. Drought and marginal or low Cu and Zn content in pasture may be the predisposing factors.

It has been suggested that the mechanism by which yeast cultures (YC), based on Saccharomyces cerevisiae, improve ruminant production is by stimulating rumen fibre digestion and microbial protein flow from the rumen. Both of these effects have in turn been related to the increases in bacterial growth in the rumen observed when YC is added to the diet. However, although it is has been shown that the effectiveness of YC in improving productivity is influenced by the composition of the diet fed (Williams and Newbold, 1990), little is known about how the ability of YC to stimulate bacterial numbers in the rumen is affected by diet composition.The effect of diet on the stimulation of bacterial numbers in the rumen by YC was investigated in the rumen simulation technique (Rusitec). Grass silage was prepared from a sward of perennial rye-grass, without the use of a preservative. Fresh grass was collected from the sward prior to ensilage and stored at -20°C. Grass (5.96 g dry matter (DM) /day) and grass silage (6.54 g DM/ day) were compared alone or supplemented with 500 mg / day YC (Yea-sacc, Alltech), in triplicate, in an experiment lasting 21 days.Four rumen cannulated sheep, allowed ad lib access to grass silage, were used to investigate further the effects of YC on bacterial numbers in the rumen in vivo. The effects of YC (4 g/ day) were investigated in a 2 × 2 factorial design with 28 day periods.