The ideal weaning dates strikes a balance between maximising profits from lamb sales and protecting ewe condition, but several factors influence the decision about when to wean.
Key points
- Strike a balance between maximising profits from lambs and protecting ewe condition.
- From about eight weeks of age lambs receive little growth benefit from ewe’s milk.
- Strategic early weaning can benefit the whole farm system.
- The minimum weaning weight is 16kgLW provided high quality feed is available.
- The quality of forages on offer is the biggest determinant of how well lambs grow post-weaning.
- Ideally ewes should be weaned at their target mating Body Condition Score of 3–3.5.
The ideal weaning dates strikes a balance between maximising profits from lamb sales and protecting ewe condition, but several factors influence the decision about when to wean.
Feed quality and availability, lamb age and growth rates, ewe condition, animal health status and lamb prices will all change over spring, so regularly assessing these variables will help determine the optimum time to wean in any given year.
Lamb growth rates peak at between three and six weeks after lambing (averaging 250-350g/day) and these growth rates can be maintained if the ewe and lamb are offered high-quality feed.
From around eight weeks of age, lamb growth rates are generally declining, and they receive very little growth benefit from the ewe’s milk.
While lambs start eating pasture from two weeks of age, they cannot fully digest it until they are three weeks old.
Lambs weaned before six weeks simply cannot make up for the lost milk by eating more pasture and lambs weaned before eight weeks will typically grow slower than lambs left on their mothers, unless high quality forage is available to them.
Weaning check
If ewes and lambs are well-fed with high quality pasture and ewes are milking well, weaning between eight and 12 weeks will reduce lamb growth rates. If lambs are within two to three kilograms of their sale weight, it would be preferable to leave them on the ewe to allow them to reach their target weight.
Lighter lambs will typically have less of a weaning check than heavier lambs.
Early weaning
Early weaning can be a flexible management tool that benefits the whole farm system. Early weaning a proportion of the flock early means ewes can be either be sold early as cull ewes or used as a pasture management tool to prepare pastures for when the main flock is weaned.
Early weaning can also benefit hoggets as it allows more time for later-lambing hoggets to regain body condition before they are mated as two-tooth.
Trials run at Massey University found 16kgLW to the minimum weaning weight, provided suitable lamb feed was available.
They found that while heavier lambs of over 20kgLW cope better with early weaning, it was the quality of forages on offer that was the biggest determinant of how lambs grow post-weaning.
Maintaining ewe condition
While the focus tends to go onto lambs in early summer, ewe condition needs to be considered to protect next year’s productivity.
Ideally, ewes should be weaned at and or above their target mating Body Condition Score (BCS) of 3-3.5.
It is expensive to try and put weight on ewes over summer especially in summer dry regions. It takes 6-7kgDM to put just 1kg onto a ewe post-weaning.
Ewes weaned at their optimum BCS can be used as a pasture management tool over summer. While the ewes at sub-optimal Body Condition can be given priority feeding on forage crops such as lucerne and summer brassicas, or better pastures. BCS can be used to efficiently allocate feed.
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