19 January 2001

Universitys plea for big head cases

WITH lambing already underway in many pedigree and commercial flocks, Liverpool University is keen to hear from any farmers who encounter the "big head" problem in lambs.

Known as hydrocephalus, the condition is being studied at the unversitys vet centre at Leahurst by Stephen Kemp and Alun Davies. They are involved in a research programme to locate a marker for the gene that controls hydrocephalus.

Affected lambs are born with the typically enlarged, domed head and thin skull bones. Parturition can be a problem and in many cases a caesarean operation will be necessary. Lambs suffering from the condition usually die at birth or soon afterwards.

The Liverpool team says hydrocephalus occurs spasmodically in individual flocks and believes it is almost certainly genetically controlled. Affected lambs occur when genes responsible for the condition are carried by both sire and dam.

Carrier status

"This means that in all cases of hydrocephalus both apparently normal parents have carrier status. It is these carrier animals that maintain the problem in the sheep population," says Mr Davies.

When carrier sheep are mated together only a quarter of lambs can be expected to show hyrdocephalus but two-thirds of the apparently normal offspring will be carriers. Even when a carrier is mated to a non-carrier, half the progeny will be carriers.

Extensive use of carrier rams will probably result in some hydrocephalic offspring being born, but it will substantially increase the number of carrier animals in the population and hence exacerbate the problem for future generations.

The researchers are urging farmers who come across the condition during lambing not to bury affected lambs but to phone and inform the research team at Liverpool University.

"If we can locate the market gene responsible for hydrocephalus it should be possible to identify carrier animals reasonably accurately and so avoid their widespread use in the sheep population."

Liverpool University says confidentiality will be observed in all aspects of information. Contact numbers are 0151-794 6103 or 0151-327 5699. &#42