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Saturday 3 December 2016

Dealing with lambing conditions

Dr Tommy Boland

Published 29/02/2012 | 06:00

A fortnight from now, lambing will be in full swing. At the moment, we are making the final preparations to ensure everything will go as smoothly as possible.

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With the use of synchronised breeding we could see as many as 50-60 ewes lambing in a 24-hour period, so advanced preparation is necessary. In addition, there are a number of experiments taking place this year under the guidance of masters students Kevin McDermott and Cormac Ryan. The experiments will add greatly to the workload and see second-year agricultural science students from Belfield help out.

At the time of writing, the twin-bearing ewes are receiving 500g/day of concentrates, with the singles on 350g and the triplets at 900g/day. Up to about 16 days before lambing the ewes receive a 14pc crude protein ration that is a three-way coarse mix of barley, citrus pulp and distillers. This is then raised to 18pc through the addition of some soya-bean meal for the final stages of pregnancy.

A number of different conditions can arise in late pregnancy which are largely or partially linked to how the ewe is being fed. Treatment can be difficult and there will be an impact on the ewe's future performance and whether or not she remains in the flock. These conditions or diseases include, but are not exclusive to, twin-lamb disease, acidosis and prolapse.

Twin-lamb disease is linked to a glucose deficiency and is similar to the condition of ketosis which occurs in dairy cows.

In essence, demands placed on the ewe for energy are greater than what her diet is supplying. She then needs to mobilise her body reserves to make up the shortfall. When body reserve, or fat, mobilisation is excessive, ketones (a by-product of fat mobilisation) build up in the bloodstream. This gives rise to symptoms including (but not restricted to) depression, apparent blindness and muscle tremors.

Treatment is very difficult as the ewe's energy demand continues to increase and her intake drops dramatically.

Prevention is much the better option.

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Twin-lamb disease can be caused by a number of factors such as excessively fat or thin ewes, or an abrupt change in diet.

Acidosis occurs when the pH of the rumen drops below its optimum level. There is much debate about the threshold pH below which acidosis is said to occur, but in reality this doesn't matter at farm level. What does matter is that the sheep are managed in such a way that the conditions within the rumen are optimised.

Acidosis is considered to be a problem with high concentrate diets, but often diets where intermediate levels of concentrates are fed are more risky.

This is the type of diet we commonly see in late pregnancy, for example, where ewes are consuming around 1kg of silage DM and 0.75-1kg of concentrates. In this situation, the concentrates can cause the pH to drop which will reduce the amount of energy the animal can get from the silage (or any other forage).

Treatment is based around returning the pH to normal, through reducing concentrate intake or feeding various buffers to raise the pH. However, the occurrence of acidosis is linked to twin-lamb disease and prolapse. To prevent acidosis it is important to build up concentrate levels gradually and feed little and often. At the very least split the feed once the level goes above 500g/day. Don't feed concentrates when the ewes are hungry. So if the ewes are out of silage in the morning, feed the silage first and then feed concentrates. Inclusion of some whole cereal grains will also help maintain conditions within the rumen.

Prolapse is a condition where there is greater difficulty in pinpointing the cause. Prior to lambing, what we see is vaginal prolapse, with uterine prolapse (putting out the lamb bed) occurring after lambing. Ewes that have prolapsed previously are more likely to do so again and should be culled from the flock.

Most farms will see some prolapse occurring. Data from Britain suggests an average occurrence of about 1pc. Anything above 2pc indicates a problem. Many causal occurrences -- such as multiple lambs and lack of exercise -- may impact on the incidence of prolapse but there is no clear relationship. Acidosis, or more accurately sub acute-ruminal acidosis (SARA), has also been blamed. SARA reduces rumen pH but not to an extent to cause clinical symptoms. In this case there can be a build up of material in the rumen which puts extra pressure on the womb, perhaps causing prolapse.

Dr Tommy Boland is a lecturer in sheep production at Lyons Research Farm, UCD. Email: tommy.boland@ucd.ie

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