Case study – Controlling leptospirosis in dairy herds

Calving two spring-calving herds in as tight a block as possible is essential for dairy farmer, Robert Wain, Simonswood Farm, Macclesfield so, when empty rates reached 25%, the farm was keen to tackle the problem head on.

The Cheshire farm runs a grass-based block calving system with a 400-cow herd on 320 acres of grazing and 360 autumn calvers on 340 acres. A recently acquired farm in Warwickshire will also be home to 250 spring calvers.

The situation on the farm has changed significantly in recent years. Five years ago, when the herd was about 700 milking cows, Mr Wain and his vet, Helen Worth from Wright and Morten, started to notice that a significant number of cows were being tested PD-positive but were failing to calve. They also felt too many services were needed per successful conception.

“Empty rates were about 25%, which for a tight block calving herd is too high,” explains Helen Worth.

As the herd had rapidly expanded with stock being bought in from a number of different sources, the team decided to investigate whether endemic infectious diseases were an issue by undertaking DairyCheck bulk milk screening, a subsidised service from Intervet/Schering-Plough.

“Results were positive for BVD and leptospirosis so a whole herd vaccination strategy was put in place with Bovilis BVD and Leptavoid-H,” Mr Wain says. “Empty rates dropped to about 17% within 12 months and performance definitely improved.”

However, as the herd was no longer expanding and stock was not being brought in, a decision was made to cease vaccination.

“Looking back, this was a mistake. Empty rates crept back up to 24% so more bulk milk screening was undertaken,” Mr Wain says.

Again, results showed the herd had been exposed to BVD and leptospirosis, which was not unexpected, says Ms Worth. “The majority of UK dairy herds will have been exposed at some stage.”

Leptospirosis is caused by infection with bacteria from the genus Leptospira. Two different strains of this affect cattle – L.hardjo prajitno and L. hardjo bovis. Leptavoid-H is the only vaccine licensed to protect stock against both strains in the UK.

“On most units, rather than affecting naïve herds, leptospirosis is present as an insidious disease causing grumbling fertility problems, and causing highly visible abortion storms and large-scale milk drop,” Ms Worth explains.

“The disease is a major cause of poor conception rates as it can cause early embryonic loss and affects early placental formation, making it more difficult to get the cow in calf.” Apart from a tangible increase in AI costs there are also losses in milk yield associated with extended calving intervals, as well as high cull rates, particularly in block calving herds.

Within the first season of restarting vaccination, there were clear improvements in herd performance, says Mr Wain. “As well as reduced culling rates, we managed to improve fertility so the spring calvers all calve within 10 weeks – this means staff concentrate on one job at a time, and do that really well.”

Freshly calved cows are turned out during the day from mid-February and anything not seen bulling or that has had an assisted calving is presented to the vet three to four weeks prior to them being served.

“Yes our system does require the vet to be on the farm very regularly at certain times of the year, but Helen is a member of the farm team and running healthy stock is essential for good herd performance,” Mr Wain concludes.

Leptospirosis – Key Facts  Clinical signs of Leptospirosis

• Bacteria settle in the reproductive tract and the kidneys. There are two important strains in the UK

• Spread when cattle are exposed to the urine of infected animals

• Infection is passed through urine, placental material or the aborted foetus of infected animals and can be transmitted through contaminated water

• Leptospirosis can be passed to humans and infected herds pose a risk to all farm workers.

• It is a notifiable disease.

• Infertility

• Fever

• Loss of appetite

• Weak calves

• Abortion – usually 6-12 weeks after infection