R.K. HOLZKNECHT, D.P. POPPI and J.W. HALES

School of Land and Food, The University of Queensland, St Lucia, Queensland, Australia

Abstract

Liveweight gain of steers grazing Meringa cowpeas (Vigna unguiculata cv. Meringa) at low (L; 2–3 expanded leaves per plant remaining) and high (H; all leaves removed) levels of utilisation and pangola grass (Digitaria eriantha cv. Stendel) was examined. The experiment was conducted in late summer and early autumn. Steers grazing cowpeas grew faster (L 1.23; H 1.17 kg/hd/d) than those grazing pangola grass (0.62 kg/hd/d) but there was no effect of level of utilisation of the cowpeas. Rumen ammonia levels were higher in steers grazing cowpeas (344 and 245 mg/L NH₃ N for L and H, respectively) than in those grazing pangola grass (113 mg/L NH₃ N).
Primary growth rate of cowpea was 74 kg DM/ha/d and comprised 50% green leaf, 45% stem and 5% dead material. The in vitro dry matter digestibility was 64, 59 and 63% and the crude protein concentration was 223, 80 and 143 g/kg DM for leaf, stem and dead material, respectively. Cowpeas did not regrow adequately to provide late autumn grazing, limiting their use over this period. We conclude that Meringa cowpea forage is of high nutritive value, promotes high liveweight gain and can be grazed intensively without any adverse effect on live-weight gain during late summer–early autumn.