The New Zealand Merino Company and Murdoch University in Australia are undertaking a study to better understand the impact of management decisions (e.g. flock size, flock density, choice of paddock) on lamb survival.
Click here to see how increasing flock size at lambing has been shown to significantly reduce the chances of lamb survival in twin-bearing ewes. That is, putting more ewes in a given paddock at lambing will increase lamb mortality.
The project team are collecting lamb survival and flock management data from farms across New Zealand and Australia to build a more comprehensive picture of how each variable affects lambing outcomes. The initial results (see below) confirm that mob size has a significant effect on lamb survival in Merino flocks.
We look forward to bringing you further results from the study over the coming months.
Impact of ewe condition on lamb survival
One of the biggest gains that fine-wool sheep growers can make is in lifting the survival rate of lambs, particularly in twins, through better allocation of feed to ewes during pregnancy. As the graph shows, twin lamb survival (blue line) is highly dependent on the condition of the ewe at lambing (whereas single lamb survival (green line) is less sensitive to ewe body condition).
Identifying twin-bearing ewes at scanning, means they can be given priority with higher quality pastures throughout pregnancy. This gives them the best chance to maintain body condition through to lambing, and is particularly important for any ewes that are in lighter condition at scanning.
By taking care of twins, gross revenue can be significantly boosted - even with the same conception rate. The following example uses the same scanning rate in both scenarios (125%). The difference is in the condition of the ewes at lambing and the resulting survival rates in the lambs - 85% vs 90% for singles, and 55% vs 75% for twins. The overall lambing percentage increases from 88% to 104% - an additional 16 lambs per 100 ewes. If the lambs are sold when they reach 25kg, at $2.50/kg, gross revenue increases from $5,500 to $6,500 per 100 ewes.