Bluetongue hits ram fertility hard in hotspot areas

Sheep farmers are being urged to fertility-test rams before tupping after a Devon veterinary practice found around half of those examined were infertile.

The warning comes as bluetongue virus (BTV) cases continue to rise sharply, with 2,878 cases recorded so far during the 2026-27 season.

Of these, 2,371 were in England, 461 in Wales and 46 in Scotland, compared with 348 cases during the whole of the 2025-26 season.

Devon has recorded the largest concentration, with 1,075 BTV-positive premises.

See also: New bluetongue map shows where virus is most active

Dr Nich Roper, director at independent veterinary practice Torch Farm and Equine in Devon, said about 800 rams have now been fertility-tested, with two vets carrying out tests every day for the past three weeks.

“We’re running at around about 50% of rams being infertile at the time of testing,” he said.

In a normal year, the practice would typically find problems in about 20%.

Dr Roper said many cases were likely to be linked to bluetongue, but fertility problems were also being found where farmers did not believe their stock had shown any clinical signs.

Rams were failing physical examinations, semen examinations or both, with striking changes seen in some samples.

“The semen may be more dilute, or it may be relatively normal, but the sperm are dead,” he said.

Vaccinated rams

Vaccinated rams were showing considerably better fertility rates, and Dr Roper rejected suggestions that BTV vaccination was responsible for the infertility being seen.

“You might get a very temporary rise in temperature with vaccination, but it is very, very temporary,” he said.

With tupping under way for some and fast approaching for many, he urged farmers not to assume a ram was fertile just because it appeared healthy.

“Get him tested. Speak to your vet and then work out a plan.”

Some rams affected by bluetongue may recover their fertility, Dr Roper added, but it was far from clear how temporary the problems would be.

Lower ram fertility could also feed through into next spring’s lamb crop, with fewer ewes getting pregnant and ultimately fewer lambs available for sale.

“The earlier you look, the earlier you check, the more you can do about it, the more options you have,” said Dr Roper.

In Wales, Dr Jim Hopkins, clinical director at IVC’s West Wales Farm Vets, said the same scale of fertility problems had not yet emerged, but warned against complacency.

“We will be in a similar situation next year,” he said. “We are just on the cusp of it now and I urge farmers to vaccinate their stock to protect them next year.”

Vaccine demand

Demand for vaccination next year already appears strong.

A National Sheep Association (NSA) survey of more than 1,400 farmers found 65% definitely intended to vaccinate against BTV-3 in 2027.

However, 40% said they had been unable to obtain vaccine this season despite trying, while 74% would consider ordering supplies in advance through their vet.

The NSA estimates that could equate to demand for about 350,000 doses.

NSA chief executive Phil Stocker said the findings showed the need for earlier planning.

“The supply chain for vaccines, from initial culture through vaccine being available on farm, is not immediate and typically takes several months.

“For farmers, vaccine planning must be treated as a routine part of the flock health plan.”