7 December 2001



The health status of dairy

cattle must not be sidelined

in the rush to restock after

foot-and-mouth. But there

are some simple measures

all producers can take to

ensure they buy healthy

stock. Jeremy Hunt reports

MILK producers restocking after foot-and-mouth must not feel guilty about asking for bulk milk antibody checks before they agree to buy replacement cattle.

Cumbria vet David Black of the Paragon Vet Group, Dalston, believes this simple insurance measure is easily justified.

"Im terrified that we could see a sudden rush of 30-50,000 dairy cows coming into Cumbria. If producers fail to subject those cattle to strict health checks, we could see an explosion of all kinds of problems."

Mr Black is concerned that producers buying-in stock will be in such a panic to restock that they will be afraid to ask vendors for full health guarantees for fear of jeopardising the deal.

"Dont be afraid to ask for health assurances from the vendor. When these assurances are not available, the cattle arent worth having anyway," he advises.

Producers buying-in cattle from many different herds should recognise it as a high risk business. In this case, he suggests a strict health check before the deal is struck and further vet checks before the cattle set foot off the wagon.

"Restocking farms should not throw away the chance to stock with high health status animals. This is an opportunity they have never had before.

"Buying-in just one cow with bovine viral diarrhoea or infectious rhinotracheitis will put the whole herd at risk. Also ensure new cows are free of digital dermatitis. You have the chance to keep your clean farm free of these bugs with all the long-term financial benefits that can bring."

But there are some steps which can be taken to avoid each of the main disease concerns, he adds.

&#42 Bovine virus diarrhoea (BVD)

BVD causes reduced conception rates and early embryo mortality when cows are infected before or during the breeding cycle. But developing embryos which contract the disease during the first three months of the cows pregnancy remain persistently affected with the virus, he says.

Vets warn that these calves, once born, provide the main source of infection. Though they appear normal they can shed virus throughout their lives without ever developing antibodies. Large numbers of calves affected with the BVD virus will survive well into adulthood. Note that in-calf cows with antibody to BVD can carry infected calves unless they were vaccinated prior to conception.

Buy from:

&#8226 Disease-free herds.

&#8226 Herds where all the breeding animals have been subject to a BVD vaccination programme prior to conception.

&#8226 Herds that can demonstrate a recent negative bulk milk antibody level.

&#8226 Herds from which a recently taken representative set of blood samples has shown to be negative for BVD antibodies.

&#42 Infectious bovine rhinotracheitis (IBR)

This is an acute virus which affects the windpipe and can cause fatal pneumonia. Adult cows suffering from IBR show a prolonged drop in milk yield, reduced fertility and abortion. The virus is spread via secretions from the windpipe.

Infected animals can shed the virus for life, particularly when under stress, even after developing an immune response to IBR.

These are the high risk animals which can bring IBR into a new herd. Although vaccination is an effective means of control, it does not stop infected animals shedding the virus at a later date. Seek vet advice when buying animals from herds of unknown disease status, advises Mr Black.

Buy from:

&#8226 Disease-free herds.

&#8226 Herds which can demonstrate negative antibody levels in recently taken bulk milk or negative blood samples in a whole herd test.

&#42 Johnes disease

Johnes is a chronic and progressive wasting condition with diarrhoea. The bacteria responsible is shed in large amounts in muck and can be found in milk and colostrum. Young animals are the most susceptible, but diarrhoea and weight loss dont usually occur until animals are at least 18-months-old.

The biggest risk of introducing infection is through buying-in infected stock. Tests on blood and muck can detect the disease, but can only be used to detect infected animals in the later stages of infection, he explains.

A test and cull programme is an inefficient means of control. In addition to the removal of infected animals the herd must also dispose of any progeny of any cow that tested positive for Johnes Disease. Vaccination can be used in heavily infected herds.

Buy from:

&#8226 Herds certified to be free of the disease.

&#8226 Herds which have been found to be negative to a whole herd blood test within the last three months – provided no test and cull policy has been underway in the previous three years.

&#8226 Herds which can provide evidence of freedom from clinical Johnes for at least five years.

&#42 Leptospirosis

Lepto can be a cause of reduced yield, infertility and abortion – usually in the second stage of pregnancy. It can be spread via contact with the urine of infected cows and via water or pasture contaminated with urine. Conformation of the presence of the disease in still-born calves can be difficult. Vaccination is an accepted means of control.

Buy from:

&#8226 Disease-free herds.

&#8226 Herds that can supply evidence of recent negative bulk milk antibody tests or whole herd blood tests.

&#42 Salmonella infection

Infection with salmonella can cause diarrhoea, abortion, pneumonia and septicaemia. Infection spreads in the muck. This is a serious health problem which has risk implications for those working with infected animals. Sampling of muck from the herd can detect salmonella infection, but there is only a 35% chance of detecting infection from a single sample. Discuss vaccination options with vet.

Buy from:

&#8226 Herds that can supply veterinary evidence that its cows have been free of the disease for at least two years.

&#42 Neospora infection

Neospora caninum is a protozoan parasite which can infect cattle and cause abortion.

Once infected cows become lifetime carriers. About 5% will have repeat abortions. Many infected cows produce seemingly healthy calves which are themselves infected, adds Mr Black.

Buy from:

&#8226 Herds which will allow you to blood test animals in late pregnancy or at calving.

&#42 Campylobacter infection

This is a bacterium affecting the genital tract causing infertility and abortion. Bulls can be infected without showing any signs and are responsible for spreading the infection. Herd records showing high service to conception intervals or calving rates below 95% where natural service is used suggests the presence of campylobacter infection. Vet advice should be sought to test and treat any new stock bull brought into the herd.

Buy from:

&#8226 Herds which can supply vet certification of freedom from the disease in the previous three years.

&#8226 Herds which offer animals only been served by AI. &#42


&#8226 Consider important diseases.

&#8226 Seek sellers assurances.

&#8226 Ask for test results.

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