Economic values of changes in energy concentration of pasture in contrasting temperate dairy regions in Australia

Abstract

The estimated metabolisable energy (ME) concentration of pasture has a significant influence on the profit of farm systems that rely on pasture as a dietary component. However, breeders of pasture plants have traditionally focussed on improving herbage yield over nutritive characteristics or ultimately feeding value. Pasture intake from two contrasting dairy farm experiments in temperate Australia over multiple years was used to estimate the potential economic benefit of changes in the ME concentration of pasture consumed by lactating dairy cows. Barley prices were used to calculate the worth or 'replacement cost' of the ME within perennial ryegrass (Lolium perenne L.). The economic values for changes in ME concentration of pasture in each year of the experiments were estimated using a deterministic model. Then Monte Carlo (stochastic) simulation was conducted, incorporating distributions of changes in pasture intake, ME concentration and replacement cost of ME to derive a distribution of the economic benefits of an increase in ME concentration of pasture. The mean stochastic results of a one unit increase in ME concentration across the year for perennial ryegrass were AU$191/ha (Terang- 'medium rainfall' in Victoria) and AU$459/ha (Elliott-'high rainfall' in Tasmania). In both farm experiments the largest seasonal contribution to the annual economic value was in the spring. In comparison, when economic values were estimated using changes in ME concentration achieved in experiments (1.74 MJ/kg DM higher in spring and 1.44 MJ/kg DM higher in summer), the economic values were AU$141/ha in spring and AU$74/ha in summer for Terang and AU$266/ha in spring and AU$187/ha in summer for Elliott. The economic values for changes in ME concentration of pasture provide an indication of potential feed cost savings for these farms. The savings estimated using Monte Carlo simulation for Terang was 9% of total variable costs for a one unit increase in ME concentration and 20% of total variable costs for Elliott. The magnitude of the economic benefits that genetic improvement in the ME concentration of pasture plants could have on Australian dairy farms warrants consideration by plant breeders developing breeding programmes.