Optimal breeding strategies for sheep should consider variation in feed availability

Large pasture growth variation across years requires changes in optimal management between years, making breeding objectives difficult to calculate. We modeled a farm with Merino sheep bred for wool and meat in a Mediterranean environment where feed availability and prices vary widely between years. We calculated profit and economic values for 6 traits by optimizing management across 5 years using dynamic recursive analysis, comparing varying to average pasture growth and prices. Profit decreased for the varying scenario but economic values increased. Economic values for yearling live weight and fibre diameter increased most and were least sensitive to uncertain pasture growth, having least effect on energy requirements. These changes shifted selection response from wool towards meat and reproduction, mostly because reproduction had a higher genetic correlation with yearling weight than wool traits. Therefore, variation in pasture growth should be considered when developing sheep breeding programs.