Bigger lambs or more lambs: The conundrum for New Zealand lamb producers

Abstract

New Zealand sheep producers generate most of their income from sheep sales, particularly lamb sales. To increase revenue from lamb sales producers have two choices, increase the number of lambs weaned or increase the weight of lambs produced and sold. Lifting the number of lambs sold requires an increase in lambs born per ewe, however this comes at a cost as these lambs are typically smaller and may not reach optimal slaughter weight within the desired timeframe. Alternatively, increasing the weight of lambs, while maintaining total feed supply constant, means that the number of breeding ewes carried on the farm may have to be reduced. This study utilises an existing bioeconomic model to examine the impact on farm productivity and profitability of increasing lambing percentage from an average of 133.5% to 140, 150 or 160%, or increasing lamb weaning weight from 30 kg and 25 kg for singles and twins respectively, by 10, 20 or 30%, or alternatively a mix of the two, i.e., 140% lambing rate and weaning weights of 33 and 27.5 kg for singles and twins, respectively. The results show that lifting lamb weaning weight, by 10, 20 or 30%, increases enterprise cash operating surplus (COS) from $291/ha to $342, $392, or $444/ha, respectively, which is more than the increases in COS from lifting lambing percentage by 10, 20 or 30%, which increased COS to $313, $345, or $368/ha, respectively. The alternative of lifting lambing percentage by 10% and lamb weaning weight to 33 kg and 27.5 kg, increased COS by $74/ha. Overall, increasing pre-weaning lamb growth was more profitable than increasing lambing percentage. Therefore, if a producer has a lambing percentage of 140% or above their focus should be on improving pre-weaning lamb growth rates rather than lifting lambing percentage.