Clinical forum: selective dry cow therapy

Abstract

Responsible use of antibiotics is essential to reduce the risk of antimicrobial resistance developing. Routine whole-herd treatment with antibiotics cannot be justified any more unless the herd has a high bulk tank cell count, in which case whole herd treatment can be justified until the cell count has been reduced. Blanket antibiotic dry cow therapy formed part of the National Institute into Research of Dairying's Five Point Plan and, over the past 50 years, has helped to reduce mastitis due to contagious bacteria. The UK average cell count is below 190 000/ml indicating a low prevalence of contagious mastitis infections. Alongside other control measures, the use of dry cow antibiotics has changed mastitis epidemiology. The majority of clinical mastitis is caused by environmental bacteria which can enter the udder during lactation but also during the dry period. The use of internal teat sealants has been proven in many studies to reduce the rate of new infection during the dry periods. There is an average reduction in clinical mastitis of between 25–30% following their use. Whole herd treatment with teat sealants is justified. The majority of cows in herds with cell counts under 200 000/ml are free from subclinical infection at the end of lactation and therefore do not benefit from antibiotic treatment at drying off. Decisions in regard to dry cow therapy should be made on an individual cow basis, with antibiotics only being administered when there is evidence to support their use.