Evaluation of options for production of large lean lambs in south–eastern Australia

The Australian grazing industry has made progress towards meeting requirements of meat processors for heavier carcass weights. However, further increases in the year-round supply of large lean lambs carries increased and uncertain financial risk for farmers. This paper examines year-to-year variability of gross margins for production of very large lean lambs, in a range of different grazing environments, using the decision support tool GrassGro™. GrassGro was used to compare systems for finishing lambs at liveweights (LW) of 42, 52 or 62 kg in three districts in SE Australia where the annual rainfall pattern varied from summer-dominant (Glen Innes, NSW), to non-seasonal (Cowra, NSW), to winter dominant (Hamilton, Vic.). Achieving these high LW required use of large ewes (average LW at maturity of 60–72 kg) and the rearing of male lambs made cryptorchid. Gross margins over 20 years and year-to-year variation in gross margins were assessed. Simulations showed that carrying lambs to heavier LW increased gross margins in all districts at lower stocking rates, even in the absence of price premiums for heavy lambs. However, at higher stocking rates, fattening lambs to heavier LW reduced mean gross margins. Carrying heavier lambs without reducing the stocking rate always increased variability in gross margins from the enterprise, mainly due to increased variability in the amount of feed supplement required. This demonstrates that to improve reliability of production and profitability in the prime lamb industry, the pricing strategy, risks and management practices associated with each environment need to be considered. Computer simulation provides a way to evaluate and optimize the design of the supply chain while taking into account regional and seasonal variability in pasture supply.