Negative approach boosts our understanding of biology

Dr Tommy Boland

Lambs at Lyons were weaned two weeks ago today and there was some evidence of the difficult start they had in life when we looked at the average weaning weights.

As we have an experimental flock, we routinely apply treatments that can have a negative impact on performance, much to the annoyance of our farm manager.

The reason for doing so is to get a better understanding of the biology underpinning important aspects of sheep farming such as lamb growth rate, ewe milk production and fertility.

When we looked at the performance of all our lambs, including those who were subjected to negative treatments, the twin lambs averaged 31kg live weight at 14 weeks of age, while the single lambs averaged 35kg live weight at the same age.

When we removed the lambs subjected to negative treatments, the twin lambs averaged 32kg and the singles averaged 36kg.

This represents growth rates of 269g/day and 313g/day respectively from birth until weaning.

Ewes were also weighed at weaning and averaged 75kg live weight. The average body condition score (BCS) of these ewes was 2.8. Some 75 per cent of the flock had a BCS between 2.5 and 3.5.

Ten per cent of the flock scored between 2 and 2.5, with 8pc above 3.5 and 8pc below 2.

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It is this 8pc below a BCS of 2 that would cause the most concern. In some cases there is an obvious explanation such as chronic lameness or a broken mouth which will result in culling.

In other situations the explanation is not so obvious, and we will look at the records to see what type of performance these animals achieved over the last year.

If one of these animals has weaned a light single lamb, then she will be removed from the flock.

On the other hand, if she has weaned two good twin lambs she will be retained in the flock, as despite her low BCS she is capable of supporting high lamb growth rates.


Ewes were screened for culling a week after weaning and 16pc of the flock were culled for reasons including mastitis, teeth problems and lambing problems, such as prolapse etc.

All our sheep have EID and we use a handheld reader as part of the normal management of the flock.

Any ewe which exhibited a problem at lambing time, such as prolapse or rejecting a lamb, was recorded on the handheld at lambing. An alert was entered at this time, so on each occasion when the ewe's EID is scanned an alarm sounds.

So when Stephen was identifying the cull ewes he walked along the race, scanning each tag and each time an alarm sounded that ewe was marked and drafted off.

This makes management much easier with a large flock, but it does take time to acclimatise yourself to using this piece of equipment as part of the normal daily manage-ment of the flock.

We have recently purchased a Pratley autodrafter from O'Donovan Engineering which is combined with a Tru-test XR3000 weigh indicator.

While there is certainly a training period involved in establishing the equipment, it offers great advantages for a flock such as ours where a lot of animal handing takes place.

A very simple example of what it can do is drafting lambs. If you set a target weight of 44kg, all lambs weighing more than 44kg will be sent one way and all lambs less than this will be sent another.

Immediately after weaning, ewes are stocked heavily on a bare paddock for 8-10 days at a stocking rate of 120 ewes/ha for this short period. We don't house ewes after weaning.

After this initial period, ewes will be used to graze out the paddocks behind the lambs, so lambs won't be forced to graze down into the lower sward levels, where the grass is less digestible.

Grass growth for the week to June 26 was 58kg DM/ha/day.

Lambs are grazing pasture with a herbage mass of 1,300kg DM/ha.

The first lambs were slaughtered last week and while numbers were small, we received €106 per head. These lambs averaged 42.2kg live weight and killed out at 47pc.

Ewes are winter shorn so there is no shearing at Lyons during the summertime.

We have yet to treat for blow-fly strike and have no problems to report at this stage.

Dr Tommy Boland is a lecturer in sheep production, Lyons Research Farm, UCD. Email:

Irish Independent

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