Tommy Boland: Why weaning too late can impact flock performance

Lambs are enjoying the last few days pre-weaning at UCD Lyons farm.

We aim to wean when the lambs are on average 14 weeks of age, which will occur next week.

On many farms the weaning is probably left too late, with negative impacts on flock performance for the current and future years.

The perceived problem is that the lamb will be unable to compensate for the reduction in milk intake by consuming enough solid feed/grass.


This might hold up if the ewe had an endless supply of milk, but by the time we get to 14 weeks of age, the contribution of milk to the daily nutrient requirement of the lamb is quite small as the ewes’ ability to produce milk has declined significantly.

This is even more of an issue in prolific flocks. The lamb is becoming more and more dependent on grass intake, so the situation we need to avoid is having ewes and lambs competing for grass as the lamb gets older.

This is particularly problematic when grass is in short supply.

Last year, we weaned the lambs at 11 weeks, with an average live weight of just over 31kg. This year our 11-week weight is 30.5kg, showing an average growth rate from birth for the main flock of 320g/day from birth.

We are happy with this performance, given the challenging grass supply situation in the spring.


When lambs are weaned, they are faced with some challenges which we need to manage to optimise weight gain and performance, and achieve of slaughter weight.

While every farm has its individual challenges, I classify the main challenges to lambs post-weaning in the following order of priority:

1) grass supply and quality;

2) parasite challenge;

3) trace element status.

Lambs clearly require adequate levels of nutrition post-weaning to optimise their performance.

We should be aiming to finish lambs from grass only as this is our cheapest source of feed, but it is essential that it is present in adequate quantities, of good quality and that lambs are not expected to graze too low down into the sward profile.

The grass towards the bottom of the sward (below 6cm) is of lower nutritional value and contains the majority of the infective parasite larvae in the sward.

This portion should be grazed using ewes or cattle.

To optimise lamb growth rate, we need to offer them about 4pc of their bodyweight in feed dry matter each day. For a 30kg lamb this equates to 1.2kg DM.

This should support around 250g of gain per day where pasture quality is high, but can be less than 100g/day where pasture is stemmy and quality is suboptimal.

Research from Lyons and Athenry shows that when we add additional species into the sward, either as a ryegrass/clover sward or a multi-species sward, lamb performance is improved.

On many farms, though, the swards will be grass-dominant and the guidelines above will help to optimise lamb performance.


Prof Tommy Boland is a lecturer in sheep production at Lyons Farm, UCD; @Pallastb tommy.boland;

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