Growth and forage intake of Hereford steers fed giant Parramatta grass hay (Sporobolus indicus) and the effects of dietary nitrogen supplements

Abstract

Giant Parramatta grass (GPG) (Sporobolus indicus var. Major), a serious weed of pastures of subtropical Australia, is poorly grazed by cattle leading to reports of low production on badly infested pastures. To provide information for cattle producers we recorded feed intake and liveweight change of steers in a 56-day study, and nitrogen (N) excretion over 5 days when GPG was fed as hay. Data were compared with those for GPG hay supplemented with urea (7 g urea/kg hay), or with urea and cottonseed meal (CSM; 750 g/steer.day), and with those for steers fed a native pasture (NP) hay, which included a legume (Aeschynornene falcata). Each steer was also fed daily a mixed mineral supplement of 35 g sprinkled on the hay. Urea increased (P<0.01) daily GPG hay intake from 4.2 to 5.0 kg/steer, but there was no significant increase in intake (4.5kg/steer) when CMS was included. Steers on NP hay had a mean daily intake of 5.1 kg/steer which was similar to that of steers offered GPG hay + urea. Urea increased daily liveweight gain from 323 to 555 g/steer (P<0.05); the addition of CSM further increased (P<0.05) the gain to 676 g/steer. Steers on NP hay had a mean daily liveweight gain of 480 g/steer. The gain for steers offered CSM with GPG hay + urea was higher than that predicted by GrazFeed (1993) for a low digestible, low NP hay, supplemented with urea and CSM. Improved production of steers through using nitrogen supplements, may provide an opportunity for cattle to use this weed as a hay or silage in pastures as part of a program to control weed ingress in subtropical pastures.