Abstract 314

Whiteman,-PC; Halim,-NR; Norton,-BW; Hales,-JW

Dep. Agriculture, Univ. Queensland, St Lucia, Qld. 4067, Australia.

Australian-Journal-of-Experimental-Agriculture-and-Animal-Hu bandry. 1985, 25: 3, 481-488; 22 ref.

A grazing trial with beef cattle was made on Paspalum plicatulum cv. Rodd's Bay, Brachiaria decumbens cv. Basilisk (signal grass) and Panicum maximum cv. Hamil, in the first year. P. maximum was replaced by Digitaria decumbens (pangola grass) in the second and third years. There were 3 stocking rates (3.0, 3.75 and 5.0 steers/ha), plots were fertilized with nitrogen 300 kg/ha, in 2 replicates. Liveweight gain was low; maximum values were 650 kg/ha for pangola grass, 640 kg/ha for signal grass and 400 kg/ha for P. plicatulum. Gain was only poorly correlated with rainfall because low winter temperatures retarded pasture growth. Correlations between gain and individual green leaf percentage in each species were high, particularly for P. plicatulum, which had only 2% green leaf in winter. Weight loss on plicatulum was therefore high in winter, and overall performance poor, even though this species had the highest percentage of green leaf in summer. Signal grass showed a higher tolerance to grazing at 5.0 steers/ha than the other grasses. Over most of the year, except in winter when only small amounts of green leaves were available, plicatulum had the lowest phosphorus percentage, sometimes below the 0.12% suggested as the critical dietary P percentage for cattle. Over all grasses, N and P concentrations were linearly related (r = 0.98). P. plicatulum was a poor grass for beef production and, for this grass and the other 2 species at this site, beef production using N 300 kg/ha could not be financially viable.