EFFECT OF MAIZE SUPPLEMENTATION, SEASONAL TEMPERATURE AND HUMIDITY ONTHE LIVEWEIGHT GAIN OF STEERS GRAZING IRRIGATED LEUCAENA-LEUCOCEPHALADIGITARIA-ERIANTHA PASTURES IN NORTH-WEST AUSTRALIA

Brahman Shorthorn steers (213+/-4.6 kg initial weight) were grazed on a pangola (Digitaria eriantha cv. Steudel) pasture interplanted with l eucaena (Leucaena leucocephala cv. Cunningham) in rows 1.8-2.7 m apart in the Ord River Irrigation Area (ORIA) in north-west Western Austral ia. The leucaena comprised a mean of 46% of the diet but ranged from 1 00% of the diet on day I to c. 18% on day 7 of a 7-day grazing period, within the rotational grazing system. It was suggested that the low h erbage allowance of leucaena may have restricted the intake of the ste ers, reducing the quantity and quality of the herbage consumed. The st eers were also supplemented with maize during the dry and wet seasons (1992 and 1992/93). The maize supplement was offered at 0, 0.5, 1.0, 1 .5 and 2.0 kg/head per day, over a 168-day period. Maize supplementati on at 1.5 kg maize per head per day resulted in an increase in the liv eweight gain of the steers grazing leucaena/pangola pastures in the dr y season from 0.73+/-0.05 kg/day (mean+/-S.E.) for no supplementation to 1.1+/-0.05 kg/day for 1.5 kg/head per day of maize. Maize supplemen tation up to 2.0 kg/day did not further increase the liveweight gain. A. high rate of substitution of leucaena and pangola intake for the ma ize supplement occurred. There was a large seasonal difference in live weight gain (mean 0.89 v. 0.63 kg/day for the dry and wet seasons resp ectively; P<0.001) irrespective of the level of maize supplementation. This seasonal difference in liveweight gain was not primarily a funct ion of the herbage on offer, but was most probably a direct function o f the effect of the seasonal temperature and humidity influencing the feed intake and growth rate of these Brahman crossbred cattle. This sy stem produced some of the higher liveweight gains recorded per hectare for a grazing system (1570-2110 kg/ha per year), as a result of the v ery good individual liveweight gains (250-340 kg/head per year) and hi gh stocking rate (6.25 head/ha).