The effect of Leucaena leucocephala on liveweight gain, thyroid size and thyroxine levels of steers in south-eastern Queensland

Abstract

Animal and pasture production were measured from 1975 to 1980 on pastures based on Leucaena leucocephala cv. Cunningham or cv. Peru, with Setaria sphacelata, at Samford, south-eastern Queensland. Pastures were rotationally grazed with stocking rates ranging throughout the year from 1.3 beasts/ha (winter) to 4.0 beasts/ha (summer). The cv. Cunningham pastures produced 427 kg liveweight gain/ha .year, and the cv. Peru pastures 358 kg/ha . year. The productivity of leucaena and its percentage in the diet of animals was consistently higher with cv. Cunningham than with cv. Peru. The average thyroid size of animals grazing year long was 50 and 147 g for cv. Peru and cv. Cunningham pastures (normal weights being � 25 g) although thyroxine levels measured in early autumn were never suggestive of serious thyroxine deficiency. Thus the higher productivity and consumption of leucaena on cv. Cunningham pastures, due to a higher density of plants and greater productivity per plant, resulted in better animal production than was obtained from cv. Peru pastures, despite the thyroid enlargement of animals grazing cv. Cunningham. It is concluded that there is potential for commercial use of leucaena-based pastures in subtropical eastern Australia.