Bioeconomic modelling to identify the relative importance of a range of critical control points for prime lamb production systems in south-west Victoria

Abstract

Whole-farm decision making is complex as many factors influence the profitability of pasture-based lamb production systems and other influences such as skills and attitudes also affect the behaviours of individual farmers. In this paper we used bioeconomic modelling to identify the relative importance of manipulating components of lamb production systems in south-west Victoria and quantified their likely impacts on whole-farm profitability. Four lamb production systems that varied in relation to the genotype of the ewes and the time of sale of the lambs were examined in the analysis. Two ‘systems’ were based on first-cross Border Leicester × Merino ewes that were mated to a terminal sire and the lambs were either sold as finished slaughter lambs at 45 kg liveweight or as stores at weaning at 30 kg liveweight. The other two ‘systems’ were based on a self-replacing composite breed (Romney × Coopworth base) and the lambs were sold as finished slaughter lambs or stores. Based on the assumptions used the analysis highlighted that the potential economic gain per unit change was high for several factors examined and the relative importance of these critical control points differed between production systems. Matching lamb turn-off (finished or store) to existing ewe genotype improved profitability by more than $100/ha or 50% and optimising pasture utilisation was also important regardless of production system. A 20% increase in pasture utilisation up to the optimum increased whole-farm profit by more than $100/ha. The impacts of improving pasture growth just after the break of season and through early winter on whole-farm profit were even greater. An extra 20 kg of pasture growth per day at this time of the year is potentially worth about $200/ha due to increases in whole-farm stocking rate. Extra pasture growth in early summer also has significant value for later lambing flocks. When farmers have optimised these factors the second-order control points were cost of replacement ewes for the first-cross system, age at first mating and reproduction efficiency in adult ewes. The management and production factors that will provide the greatest return on effort for individual farmers will depend on the potential economic gain per unit change in the target factor, their current management and production levels and the ease with which the management change or increase in production potential can be achieved in the farming system.