Studies on the nutrition of ruminants. I. Substitution of maize by milled barley straw in a beef fattening diet and its effect on performance and carcass quality

Abstract

Sixty-four yearling Friesian steers, in eight groups with eight animals per treatment, were fed on pelleted diets containing ground barley straw, maize and soya bean meal. The percentage of straw in the diets varied from 0% to 50% and the crude protein was adjusted in all diets to 12% on an air dried basis. Levels of 0, 10, 20 and 30% ground straw were tested in 1963–4 and 20, 30, 40 and 50% in 1964–5. Growth rates in the range of 8·28–9·49 kg. per week were obtained, with growth rate falling significantly (P<0·05) by 0·36±0·15 kg. per week for each 10% increase in straw in the 1964–5 trial; the differences between treatments in the 1963–4 trial were non-significant. The efficiency of food conversion varied from 6·5:1 for 0% straw to 7·7:1 for 50% ground barley straw. Feed intake increased as the percentage of straw in the diet rose above 20%. Regressions relating those carcass measurements in which differences between groups were significant to the percentage of straw in the diet were not significant except that for eye muscle area (P<0·05). Neither carcass nor meat quality differed significantly in animals given 20 % and 50 % ground straw. The results of digestibility trials with male hoggets showed a linear depression in the digestibility of diets as the percentage of straw increased. The results are discussed in relation to previous knowledge of the factors affecting the voluntary feed intake of ruminants. Agricultural Research Council, 1965. Recommended procedures used in the measurement of beef cattle and carcasses. H.M.S.O., London.