Animal production from a Sorghum almum pasture in south-east Queensland

Abstract

A grazing experiment on Sorghum almum pastures, one of which received 200 lb nitrogen an acre a year, as urea, was carried out at Lawes in south-east Queensland. Pastures were grazed continuously at three set stocking rates : 1 beast to 1 1/2 acres, 1 beast per acre, and 2 beasts per acre. Grazing commenced 3 1/2 months after sowing and continued for two years. Mean liveweight production over the whole period at the medium stocking rate of one beast per acre was 0.92 lb a head a day. Production was closely related to stocking rate : gain per head decreased and production per acre increased as stocking rate increased. Nitrogen fertilizer increased animal production at the heaviest stocking rate. Seasonal pattern of animal production was influenced by stocking rate, but, in general, a winter--early spring period of small gains or losses of weight was followed by a rapid increase in late spring--early summer, with the rate of gain decreasing from mid-summer onwards. This followed the seasonal pattern of pasture production : little or no production over the cool dry winter, but high yields of forage during summer. No close relation was detected between liveweight gain and green forage available in the period of rapid increase in liveweight. During the phase of declining pasture and animal production, liveweight increment was related to available pasture expressed as green material minus S. almum stem. Crude protein content of unfertilized S. almum varied from 15 per cent for green material in spring to 2.5 per cent for the dry forage available in winter. Urea increased both yield and protein content.