The recumbent ewe
Abstract
The recumbent ewe around lambing time is a common presentation. There are a number of nutritionally-related conditions often seen in sheep at this critical time during the production cycle which may cause recumbency including hypocalcaemia, pregnancy toxaemia, listeriosis and hypomagnesaemia. Differentiation of these various conditions can be achieved on the basis of detailed clinical examination and history, backed up by appropriate laboratory biochemical analyses using parameters such as β-OH butyrate and calcium. However there will often have been prior treatment by the farmer which may complicate a clinical diagnosis, and there is often overlap between the various conditions in terms of clinical presentation and disease incidence. The focus is therefore on achieving a correct diagnosis, giving the farmer a simple treatment plan for recumbent ewes, and implementing preventative measures.
The recumbent ewe around lambing time can be frustrating for both the farmer and veterinary surgeon, as they can take up a lot of valuable time at a very busy time of year. The most common causes of recumbency in ewes around lambing time are related to nutrition: either as a result of the high metabolic demands of the ewe (for example hypocalcaemia, pregnancy toxaemia and hypomagnesaemia) or feedstuffs (for example listeriosis and rumen acidosis). Careful clinical examination and history is required to determine the most likely cause, although clinical biochemistry can provide cost-effective laboratory confirmation of the diagnosis.
Hypocalcaemia is commonly seen in ewes in late pregnancy (last 6 weeks of gestation), and may also occur sporadically in early lactation. The pathophysiology is similar to that of milk fever in cows, in that it occurs when the calcium requirements for pregnancy and lactation are not met by dietary calcium absorption and mobilisation of skeletal calcium reserves, and there is a failure of blood calcium hormonal regulation mechanisms. It is more common in older sheep (3-crop or older), and ewes in any body condition may be affected. In sheep, it is frequently associated with stressful husbandry events (e.g. housing, movement in-bye, dog worrying, delay/change in feed: Figure 1) and may thus occur as ‘outbreaks’ with multiple ewes affected.
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