Changing the sex ratio of lambs may alter gross margins in sheep flocks

The proportion of male to female lambs weaned has the potential to alter flock performance. A simulation study compared the gross margins resulting from altering the proportion of wether or ewe lambs in a crossbreeding (Merino ewe producing crossbred lambs) flock and in a self-replacing Merino flock in southern New South Wales for the period 1971-2011. The mean gross margin was increased with more ewe lambs when a price premium was obtained for ewe compared with wether progeny, but was increased by more wethers if ewe and wether lambs were sold at the same age. The particular management and price variables used have a large impact on whether an increased proportion of ewe or wether lambs will increase or reduce gross margins. Producers need to consider the market options for their enterprise and systemic effects on production and costs before skewing the sex ratio of their flock.