The effects of a barley beef diet without (control) and with a yeast culture (YC) on rumen fermentation, in vivo diet digestibility, nitrogen retention, live-weight gain and food intake were evaluated using 13 Limousin × British Friesian bulls per treatment. The YC was composed of the yeast species Saccharomyces cerevisiae and its growth medium dried in such a manner that it maintained its fermentative capacity. The addition of YC significantly increased the concentration of acetate (P < 0·05) while propionate concentration tended to be higher for bulls given YC (P > 0·05). The acetate: propionate ratio remained unchanged. Concentration of total volatile fatty acid (VFA) was significantly higher in YC bulls compared with control bulls (P < 0·05). The in vitro studies using the Menke gas test confirmed these findings. Mean in vitro gas production in bulls receiving YC was lower than that in the controls (P < 0·05) and methane production was significantly reduced by the addition of YC after 12h (P < 0·01). Ruminal ammonia concentrations were not affected by treatment but ruminal pH was significantly depressed by the addition of YC (P < 0·05).Apparent digestibility of dry matter, organic matter, crude protein and neutral-detergent fibre were unaffected by treatment but tended to be higher with the control diet. Nitrogen retention was not affected by the addition of YC and mean values for allantoin excretion and plasma urea were similar.In a 28-week feeding trial, dry-matter intake was significantly greater for bulls given YC (5·55 kg/day) than for control bulls (5·32 kg/day, P < 0·05) but average daily gain, 1·55 and 1·58 kg/day for control and YC respectively, and food conversion efficiency were not improved significantly by YC (P > 0·05).

With the advent of twinning in beef cows there is a need to obtain information on the nutritional requirements of these animals during the last three months of pregnancy and to assess the effects of pre-calving nutrition on cow and calf performance in the subsequent lactation. Three experiments have been carried out With 10, 9 and 14 multiple bearing Hereford x British Friesian cows. In each experiment a comparison was made With single bearing cows but the results from these animals are not considered in this paper. The cows were given different energy intakes in a factorial arrangement with low or high levels of UDP over the last three months of pregnancy. After calving all cows were given 125 MJ ME/d for the first 12 Weeks of lactation and performance monitored to assess any carryover effect of pregnancy nutrition.Similar diets were fed during the last three months of pregnancy in all three experiments. The diet containing a low level of UDP (0.19 of total protein) consisted of barley straw, barley grain, molassed meal and urea. While that With a high UDP content (0.33 of total protein) contained barley straw, barley grain, malt distillers dark grains and special propietary cubes.

Hormonal anabolic compounds are used in certain countries to improve the efficiency of meat production from ruminant animals. The combination of trenbolone acetate (TBA) and oestradiol-17/? (OE 2 ) has been shown to be particularly effective in stimulating growth in cattle (e.g. Galbraith & Topps, 1981). These improvements in growth have been associated with increases in nitrogen retention and changes in protein metabolism within the animal. The present study therefore investigated the effect of implantation with TBA + OE 2 on the growth and metabolic response of growing steers to alterations in protein nutrition. METHODSTwelve British Friesian steers aged approximately 15 months were housed in individual stalls and allowed 6 weeks to adapt to experimental conditions. The animals were then paired according to live weight and one of each pair allocated to be implanted subcutaneously on the upper surface of the ear flap with 140 mg TBA + 20mg OE 2 ('Revalor', Hoechst, U.K. Ltd). Their initial mean live weight (±S.E.) was 439 ±6-9 kg. The steers were offered diets containing an estimated 107 MJ metabolizable energy per day and differing in rumen degradable (RDP) and undegradable (UDP) protein as follows: day 0-28 (period A), 0-86 and 0-18; day 29-56 (period B) 0-99 and 0-51; day 57-84 (period C) 0-86 and 0-18. The diets were based on grass silage, bruised barley and sugar-beet pulp in the ratio in the dry matter of 1 -0:0-65:0-65 respectively (periods A and C). The diet was supplemented in period B with a mixture (ratio 1:1) of soya-bean meal and white fish meal. The rumen degradability of this mixture was determined by Dacron bag technique utilizing a 12 h incubation in the rumen of a fistulated cow. The degradability coefficients of the other dietary components were estimated from Scottish

Previous work has shown that treating moist grain with ‘Farmline’, a formalin acetic acid mixture, affords some protection of protein and perhaps starch from rumen degradation. A comparison with and without ‘Farmline’ treatment investigated the protection afforded to dried barley.

Supplementation with Yea-sacc - yeast (Saccharomyces cerivisiae ‘1026’) and its growth medium or with Avotan - an antibiotic feed additive has been found by several workers to alter rumen fermentation patterns and animal performance. This experiment investigated the effect of inclusion of these supplements on their own or in combination in the concentrates of silage fed steers on rumen fermentation and animal performance.