The objectives of this study were to determine the effects of cellulase (from Trichoderma longibrachiatum) combined with formic acid, applied before ensiling, on the subsequent concentration and composition of the cell wall and on the extent and rate of in situ cell-wall digestion of orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.). Treated and control forages of both plant species were ensiled for at least 60 d before being ruminally digested by two fistulated cows. Analyses of NDF, ADF, and acid detergent lignin were conducted sequentially on original and digested samples. Data were fitted with a first-order, nonlinear model to estimate extents and rates of digestion of potentially digestible NDF, cellulose, and hemicellulose. The concentration of indigestible residue and the discrete lag time before digestion were also determined for the cell-wall components. After ensiling, the mean NDF concentration of treated silages was 19% lower than that of control silages; the effect was greater for orchardgrass than for alfalfa. The extent of digestion of NDF, cellulose, and hemicellulose, respectively, was 33, 37, and 27% lower for treated silages than for control silages. Treatment effects on the extent of digestion varied between plant species. Cellulose from treated orchardgrass was digested 19% more slowly than cellulose from the control silage. Indigestible residue concentrations of NDF, cellulose, and hemicellulose, respectively, were 7, 8, and 7% lower in treated silages than in control silages. Thus, extensive cell-wall degradation by cellulase during ensiling resulted in less digestible cell-wall material for ruminal digestion but greater total cell-wall degradation, including that during ensiling and ruminal incubation, especially during early digestion in the rumen.

The trace element status of crossbred Friesian x zebu (Boran) and local zebu cattle in the Selale highlands of Ethiopia was evaluated during the rainy and dry seasons of 1989 and 1990 in terms of the trace element content of soils, feeds, blood plasma and faeces on 25 randomly selected farms. Liver samples from animals of local breeds from a slaughter house were collected during the rainy and dry seasons of 1990 and analysed. Soil Fe and Mn were found to be high. Iron contents of all feeds were extremely high and Mn contents were higher than the dietary requirement. A large proportion of feed samples were deficient in Cu and zinc. There were wide variations in the concentrations of these elements among the soil and feed samples. Blood plasma Fe (P < 0.001) and Cu (P < 0.01) values differed significantly between the years. Plasma samples collected during 1990 contained lower mean Cu than 1989. The effect of season was statistically significant (P < 0.001) for all the trace elements. More than half of the animals were found to have low plasma Cu and Zn during the rainy season. Due to lack of any correlations between soil, pasture and blood plasma it is suggested that analyses of soils and pasture are not reliable for assessing the Fe, Cu and Zn status of grazing cattle in the highlands. Analyses of liver and blood appear to provide better indices.

The macro mineral status of cattle in the Selale highlands of Ethiopia was evaluated during the rainy and dry seasons of 1989 and 1990 in terms of mineral concentrations in soils, feeds, blood plasma and faeces on 25 farms. Bone samples from animals of local breeds from a slaughter house were collected during the rainy and dry seasons of 1990. Soils were analysed for pH, organic matter, Ca, P, Mg, Na and K. The results indicated wide variation in the concentrations of minerals on different farms. Available feeds in the area consist of pasture, hay, the straw of barley, oats and teff, and the grains of barley and oats. Pasture grass and other feeds were found to be deficient in Na, P and Mg in relation to dietary requirements. Analyses of blood plasma from crossbred and local cattle showed that a number of samples contained P below the critical level of 1.45 mmol/litre. Effects of year and season were significant for Ca, P, Mg and K. The effect of age was significant for P (P < 0.001). Faecal analyses revealed that about 80% of animals were deficient in Na. Wide variations in the mineral content of soils and lack of significant correlations among soil, pasture and blood plasma indicated that soil and pasture analyses are not reliable in assessing macro mineral status of grazing cattle in this environment. Analyses of bone and blood for Ca and P, blood for Mg and faeces for Na appear to provide better indices.

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