These are eggs that could contribute to the potential of the ewe flock and the scanning percentage.
There are many factors that vary between farms that impact on [ewe flock] potential such as ewe breeding, timing of mating, and topography but the focus here is performance within the existing ewes and current farm resources.
The key management factors that come into play are weight of the ewe at mating, feeding level over mating through to scanning, and ram quality-quantity.
There are many factors that vary between farms that impact on this potential such as ewe breeding, timing of mating, and topography but the focus here is performance within the existing ewes and current farm resources.
Assuming a scanning of 150% then the ovulation rate would have theoretically been 178%. This means that an average ewe would have the ability to generate $170/ewe of lamb at weaning.
The lost potential from mating to scanning is therefore $26 of lamb/ewe mated – assuming a 32kg lamb at weaning worth $3/kg liveweight or $96.
To improve the potential, barren ewes need to be minimised and ewes well fed through to day 50 of pregnancy.
The next component is the losses from scanning to docking. On average, 18% of the potential lambs at scanning do not get to the docking-tailing board, or 27 lambs per 100 ewes in this case.
This means that of the $144 of lamb per ewe at scanning a future $26 of lamb is lost before docking.
Some of these losses post-scanning are because of ewe deaths, usually in late pregnancy (an average of 1% of ewes).
Table 1 highlights that as scanning percentages increase the cost of the loss of potential lambs also increases. This means that on average there is $50-$70 worth of potential lamb being lost per ewe.
In reality some farmers are minimising this loss while other farms continue to be challenged.
The largest gains are to be made in the period from scanning to weaning and in particular lambing. With lambing almost here farmers will have strategies in place to achieve good lamb survival from their ewes.
The challenge is to work out what is the cost of these potential lambs for each individual farm.
- Brendan Brier, Brier Ag Consultancy
