Monday 26 September 2016

Sheep: Weaning stresses can hit lamb growth

Tommy Boland

Published 22/06/2016 | 02:30

Lambs are due to be weaned.
Lambs are due to be weaned.

The rainfall of recent days has provided the ideal stimulus to grass growth and blow-fly strike, both of which excel in warm wet conditions of late.

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As with a lot of sheep ailments, prevention is better than cure and this certainly applies to blow-fly strike. It is a real pain to be taking in sheep on a daily basis to deal with maggots so preventative treatment is the preferred option.

However, one needs to be very careful to keep withdrawal periods in mind when selecting products. These can range from one week up to five or six weeks.

Even at a modest post weaning performance of 150g per day, lambs will achieve a live/weight gain of 6.3kg in a six week period, so we must be very conscious of this in selecting a suitable product to use.

Now is the time of year when most lambs will be weaned and our lambs are due for weaning this week. This is always a stressful time on the animal and it presents a significant challenge in the growth of the lambs.

Post weaning a number of factors will challenge lamb growth rate with three important ones being energy supply/feed quality, parasite challenge and trace element nutrition.

The weaned lamb still has a very high potential for growth, but in many instances this is not achieved due to issues with one or more of the factors listed above. First focus should be on the quality of the grass available to the lambs.

Low herbage mass (leafy) swards should be made available and lambs should not be pushed in terms of grazing low down into the sward horizon.

The quality of the grass decreases the closer it is to the ground, so lambs should be moved on when sward height is in the region of 5.5cm to 6cm, and then ewes used to clean out the sward to encourage quality regrowths.

Parasite control

Parasite control is another key issue. While many farmers may have had some hesitancy, the inclusion of faecal egg counting in the STAP scheme was a very positive move, if for no other reason it got people thinking about when they should dose.

The practice of calendar dosing should be gone and instead we should be dosing in response to parasite challenge.

I appreciate there are plenty of issues here in terms of time taken to receive a result of a faecal egg count, but to ensure the long term efficacy of the drugs used to control parasites we need to re-examine how we use these.

Thirdly, we need to focus on mineral nutrition and this is often a contentious area. It is often the first issue which is blamed for poor, perceived or otherwise, animal performance, and minerals are viewed as a panacea which will cure all ills.

There is no argument that where a mineral deficiency exists, performance will improve when that mineral is supplemented.

However, there is probably a level of over supplementation taking place and, while not detrimental to animal performance in most cases, there will be a cost implication.

It's likely that in many situations the first limiting factor to lamb performance post weaning is grass supply and quality and the reality is most farms are not set up to maximise these factors.

But I would also pose the question: how many people know how their animals perform?

A very simple option is to select a number of lambs at weaning (15-30) and weigh them each time the flock passes through the yard.

This will allow the identification of poor growth and even aid in understanding what is driving this.

These lambs should be reflective of the variation within the flock, otherwise it will be a futile exercise.

Dr Tommy Boland lectures in sheep production at UCD's Lyons research farm at Newcastle, Co Dublin.

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