14 June 2002

Dry cow therapys a saver

By Richard Allison

USING the correct dry cow therapy to prevent coliform mastitis in the following lactation can save up to £7 a cow, says one vet researcher.

More than 70% of gram-negative mastitis (see panel) seen in early lactation is due to infection during the dry period and first few days of lactation, says Andrew Bradley of Bristol University vet school.

"At one extreme, these bugs can infect the udder, remain dormant and lead to mastitis 250 days later. But most occur in the first three months of lactation.

"Gram-negative bugs are generally associated with environmental mastitis cases. But most dry cow antibiotic treatments offer limited control against gram-negative infections. They were originally developed for controlling gram-positive infections, such as Strep uberis and Staph aureus."

In one university study, a dry cow therapy (Cephaguard) with extended activity against gram-negative for up to nine weeks was tested. Using this broad spectrum antibiotic treatment, instead of a standard product, led to a 50% reduction in E coli type mastitis in the next lactation. This equated to 28% fewer cases of mastitis, says Dr Bradley. "This shows that unless the correct dry cow strategy is adopted, mastitis treatments during lactation will have little effect on preventing a large proportion of cases. The cost benefit of using the correct treatment is £680 in a 100-cow herd, which more than covers the cost of dry cow antibiotic treatment."

To improve effectiveness, Dr Bradley recommends a targeted approach for preventing mastitis. "Split the herd into two groups, based on high or low individual somatic cell counts. This can be carried out using NMR milk testing data or a California Milk Testing kit at drying off.

"Cows with high counts before drying off are likely to be already infected with gram-positive bugs and must be treated to cure this infection with a product with extended activity against these bugs."

Those with low cell counts only require preventative treatment with a product with prolonged activity against both gram-positive and gram-negative bugs. "But it is not always clear which treatment to use on certain cows. You may have to compromise by deciding whether gram-positive or gram-negative bugs pose the greater risk.

"In future, internal teat seals could be used instead for cows with low somatic cell counts, removing this compromise. This is because internal teat seals, like those used in New Zealand, are effective against both groups of bugs."

These seals have a toothpaste-like consistency and are infused up the teat canal where they form a physical seal preventing infection. Recent work shows that teat seals are more effective than broad-spectrum dry cow treatments, says Dr Bradley.

This could be particularly useful for organic producers, as it offers a more effective alternative to long lasting dry cow antibiotics, provided they gain accreditation from the various organic schemes. This would also allow conventional producers to cut their reliance on antibiotic treatments, he says. &#42