A stochastic farm model to simulate dairy farms and the segregation of cows to produce milk with different concentrations of unsaturated fatty acids

The model was used to simulate: (1) a population of 1,820,000 cows in 5600 farms (AVE farms), and (2) the establishment of a farm (120 ha) for the production of milk high in UFA through the segregation into a herd of the top 325 (2.71 cows/ha) or 353 (2.94 cows/ha) cows for fat UFA concentration (UFA2.71 farm and UFA2.94, farm, respectively). The simulations were repeated 1000 times and 95% confidence intervals were estimated by bootstrapping methodology. On average, the UFA2.71 and UFA2.94 farms produced milk with 23.6% more UFA than AVE farms. However, cows on the UFA2.71 and UFA2.94 farms had significantly lower yields of fat (both −48 kg, P < 0.05), protein (−24 and −23 kg, respectively, P < 0.05) and milksolids (−73 and −72 kg, respectively, P < 0.05) than cows on AVE farms. Under a milk payment system that pays for yields of fat ($3.80/kg) and protein ($9.67/kg), and penalises milk volume (−$0.03/l), the UFA2.71 and UFA2.94 farms had significantly lower operating profit (−$872/ha and $946/ha, respectively, P < 0.05) than AVE farms. These results indicate that farm profit would be adversely affected unless there is a premium for fat UFA concentration.