M.S. LORIMER

Toorak Sheep Field Research Station, Queensland Department of Primary Industries, Julia Creek, Queensland 4823.

Abstract

Oesophageal extrusa from Merino wethers grazing Mitchell grass (Astrebla spp.) pastures in north-west Queensland were analysed for nitrogen content, proportion of green material in the diet and digestibility. Faecal samples were analysed for nitrogen content and intake was calculated from digestibility and faecal output data
Maximum organic intake values were 0.45 kg day^-1 during the latter part of the dry season, compared with minimum values of 0.11 kg day^-1 immediately after the start of the wet season rains.
A poor relationship occurred between the nitrogen content and the proportion of green material in the diet selected.
The quantity of nitrogen excreted daily in the faeces was relatively constant at 5–8 g day^-1, however, the quantity of nitrogen ingested varied considerably from maxima of 19–22 g day^-1 to minima of 3–6 g day^-1. In 1972 the sheep were in a state of negative nitrogen balance for the last 2–3 months of the dry season.
Average liveweight was relatively constant at 40–45 kg except for the period immediately after the start of the wet season rains when minimum values of 32 kg occurred.
Clean wool production, fibre diameter and linear growth rate all responded to the new season's pasture growth, but at different rates. The annual average fleece-weight during the three year trial period was 3.8 kg head^-1.