Evaluation of oat forage for finishing prime lambs on the Northern Tablelands, New South Wales

Abstract

In 1967 at Armidale, New South Wales, oats (Avena sativa cv. Cooba) were grown with or without 180 kg N ha-I and rotationally grazed on a three paddock system from July 13 to November 16 with Border Leicester x Merino lambs. Stocking rates were 20,40 or 60 sheep ha-1 (experiment 1). In 1968 (experiment 2) oats were rotationally grazed on either a three or four paddock system at stocking rates of 20, 30 or 40 lambs ha-1. Grazing began on either June 6 or July 17 and terminated on November 20. The rotational grazing systems allowed for a grazing period of two weeks and regrowth periods of four or six weeks. Application of nitrogen increased the quantity of dry matter available prior to grazing in 1967 by 20 per cent but did not affect regrowth rates during winter and early spring. In 1968, approximately 33 per cent more forage was available prior to grazing in mid-July than in early June. There was little effect of grazing management on the rate of regrowth. In both years, regrowth rates were low during winter and carry over residue was required to provide a continuity of available forage. Liveweight gains of lambs during winter and early spring reached 170 to 200 g head-1 day-1 at stocking rates of 20 or 30 sheep ha-1 for the early and late commencement of grazing treatments respectively. Lower gains to 120 g head-1 day-1 were recorded for six to eight weeks at higher stocking rates but subsequent liveweight losses occurred; these being greater if grazing commenced early. Neither N nor grazing management system materially affected liveweight gains. Approximately 1.5 kg available dry matter head-1day-1 was required at the start of each fortnightly grazing period to ensure maximum liveweight gains