Johanna M. Pluske

Economic Management of Anthelmintic Resistance: Model and Application

The increasing prevalence of anthelmintic (drench) resistance in gastrointestinal parasite populations is decreasing the profitability of the Australian sheep industry. Refugia management can delay its development by not exposing a proportion of the worm population to chemical control. A dynamic-optimisation model is used to assess the economic value of refugia for management of the worm species Teladorsagia circumcincta and macrocyclic lactone drenches in an application to Western Australian sheep flocks. A low rate of refugia (2 per cent) is most profitable under standard circumstances because it slows the development of resistance, but also reduces the proportion of the flock not exposed to chemical control. Frequent drench application should remain the primary method of control. However, its efficacy should be preserved through refugia management, rather than greatly reducing treatment frequency.

Water management as a future necessity in sheep feedlots

Improving water management in rural towns such as Wagin, Western Australia, will decrease infrastructure damage caused by water and salinity and produce a ‘new water’ resource. The aim of this paper is to predict feedlot water demand using a bioeconomic model, H20Sheep, to determine if using such a ‘new water’ resource could be a viable option for this production system. Wagin (–33.3075 S, 117.3403 E), a township south-east of Perth, was chosen as the specific location for a sheep feedlot producing prime lambs. In this paper, the H20Sheep model was used to show how feedlot returns are influenced by the price of water, different feeding regimens and climate change. This was done by integrating feed and water intake of lambs, general feedlot water use and waste disposal. To show relative sensitivity of changing other model parameters that are not directly connected with water, changes in the purchase and sale price of lambs were also investigated. As might be expected, H20Sheep shows that returns from a sheep feedlot enterprise can be extremely sensitive to changes in lamb purchase (just over 7% increase will result in negative returns) and sale prices (a 4% decrease will generate a negative outcome). With respect to water, the findings indicate that, while increases in water use in the feedlot and price have to be greater than the increase in relative price of sheep, monitoring the biological parameters associated with water as well as water prices is still important both from a management and an economic perspective. Hence, if towns involved in the Rural Towns – Liquid Assets project, such as Wagin, decide to sell their water, the relevant policy makers should ensure that the sale price enables an effective water management system for the town and is also attractive to end-users such as feedlots.