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VET’S DIARY: Ewe nutrition is the key to successful lambing

While it might not feel like it, for us farm vets, spring is officially here, writes Joe Henry.

There may still be snow on the ground in places but it is coming up to lambing time for our early lambers.

In order to do all that we can to ensure a successful lambing time, a key consideration for us and our farmers is pre-lambing nutrition. In the last six weeks of pregnancy the ewe faces extreme demands on her body as 70 per cent of lamb growth takes place during this time. Poor nutrition in the ewe in the last four to six weeks of pregnancy can lead to twin lamb disease, hypocalcaemia and mastitis in the ewe. For the lambs, poor ewe nutrition can lead to hypothermia (which can be a particular hazard for those lambs born earlier in the season), watery mouth/rattle belly, joint ill (navel ill), pneumonia and scour.

It is vital that the ewe has enough to eat and the means to be able to eat and drink enough so together with the farmer we consider a number of different factors including their grazing, housing, trough space, water availability, ewe health and lamb numbers.

One procedure that can make a huge difference to ewe feeding is scanning. Scanning is crucial because it can identify barren ewes early and so those that are not pregnant do not receive supplementary feeding. You can identify single-bearing ewes early and they can be fed accordingly. They may get sufficient energy from forage alone and do not need supplementary feeding and those ewes that are having multiple pregnancies can be fed and monitored separately.

Another advantage of scanning and identifying foetal numbers can help as part of a farmer’s worming plan, if wormers are to be used at lambing time.

It is also important for us to assess a ewe’s body condition score (BCS). Body condition scoring is a numerical scale used to evaluate the amount of fat on the sheep’s body. The ideal BCS is between 2.5 and 3.5 for highland and lowland breeds. For those ewes in poorer condition then supplementary feeding needs to start earlier. On the other hand, if the ewe is in good condition then some energy deficits can be overcome by relying on the ewe’s own reserves.

A ewe is only able to consume two to two-and-a-half per cent of her body weight in dry matter so all her nutritional requirements for this period of intense growth must be contained in this percentage. The make-up of the diet is, therefore, the most important factor. The majority of farms will use a combination of grazing, forage (hay or silage) and commercial concentrates.

The only way we can accurately assess the ewe’s diet is to take a blood sample to judge how they are responding to the diet. This is best done approximately three weeks before lambing, ideally with a minimum of 10 ewes. Results from the analysis will show if the energy or protein content of the diet needs adjusting.

In the late stages of pregnancy some ewes may develop twin lamb disease and we consider this a warning that the flock is under nutritional stress. Survival rates of ewes with twin lamb disease are generally poor but can be better with aggressive treatment. The options for treating twin lamb disease are glucose supplements, steroids and non-steroidal drugs (NSAIDs). However, given that the major reason for the occurrence of twin lamb disease is the presence of the lambs, inducing the ewes can often be the best means of a cure. However, this option is not taken lightly and is always considered on a case-by-case basis.

What we hope for now is that all the snow for this winter has been and gone but you just cannot predict. Last year we had an unseasonably nice March which was great for the early lambers but was followed by snow in late April which led to greater lamb losses for late lambers.

 

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