Evaluation of pasture for beef cattle from measurements of cell wall in separated leaf and stem fractions

Abstract

SUMMARYThree pastures, pangola–clover, setaria, and tropical grass–legume, were grazed for a 9-month period by 12 steers of initial live weight of 199 kg on each. For the first 5 months live-weight gains were, respectively, 1·2, 0·76 and 0·43 kg per day, mostly higher than could be expected for estimated dietary energy concentrations of 10·1, 8·9 and 8·7 MJ of metabolizable energy (ME) per kg of dry matter. The high live-weight gains were not explained satisfactorily by dry-matter intakes as measured from faeces voided and dietary digestible dry matter, but were possible if published values for the requirements of ME for growth and fattening were too high. Cell wall, in vitro digested cell wall and nitrogen in separated leaf and stem fractions were useful indices for evaluating pasture for grazing cattle, but they did not predict live-weight gain.

Inter-relationships between pasture growth and senescence and their effects on live-weight gain of grazing beef cattle

“…Given the closeness of fit of the model to the data, an understanding of causal factors that regulate live-weight gain can be helped by considering how the three independent variables could have been accommodated in the model's quadratic form. This can be done for cell wall in green-grass leaf and pasture dry matter on offer; at high cell-wall values in green-grass leaf such as were found in setaria, the even higher cell-wall values in green-grass stem could favour selective grazing of leaf (Moir & Ebersohn, 1983). Although pasture on offer was negatively correlated with dietary energy (Ebersohn & Moir, 1984), a high pasture on offer would benefit live-weight gain when leaf is selected almost exclusively.…”

“…Paddocks in which the enclosures were situated were not grazed until there was enough pasture to maintain live-weight gain at an anticipated level, and so, in contrast to pasture in enclosures, dead plant material was present. Measurements that had been made of the non-green grass content of the pastures and that of oesophageal extrusa from cattle grazing them (Moir, Ebersohn & Evans, 1982;Moir & Ebersohn, 1983), when considered in conjunction with values for pasture growth in enclosures, enabled the relative importance of plant growth and senescence in explaining live-weight gain to be assessed. Results are presented in this paper.…”

Effect of pasture growth rate on live-weight gain of grazing beef cattle

“…Data were drawn from experiments conducted at the Coolum Research Station as described by Moir et al (1982) and Moir & Ebersohn (1983). Only data from pastures that supported live-weight gain were used.…”

“…Large variation in the magnitude of live-weight gain of beef cattle grazing tropical pasture, for little or no change in dietary-energy concentration, has been reported by Moir, Ebersohn & Evans (1982) and Moir & Ebersohn (1983). High live-weight gain was not explained by intake; for the amount of faeces voided digestibility would need to have been much higher than is normally attributed to tropical pasture.…”