Abstract
The objectives of this study were to compare the efficacy of 6 different dry-cow intramammary antimicrobial products for the treatment and prevention of mastitis during the dry period in a well-managed high producing Friesland dairy herd, and the influence of treatment on the somatic cell count (SCC) of cows during early lactation. One of 6 dry-cow intramammary antimicrobial products was randomly allocated to 162 cows due for drying off over a period of 14 months. All cows were sampled twice prior to drying off, and twice after calving for the determination of SCC and presence of microorganisms. The quarter prevalence of pathogens at drying off and post-calving, the overall quarter cure rate and the rate of new intramammary infections occurring during the dry period were determined. The overall quarter prevalence of intramammary infections (IMIs) at drying off was 29.78% and after calving 22.22%. There was a statistically significant difference (P < 0.05) between the prevalence of major and minor pathogens at drying off (7.87% and 21.91%) and at calving (4.47% and 17.75%). The most prevalent pathogens isolated at drying off (21.14%) and at calving (16.98%) were coagulase-negative staphylococci (CNS). The quarter cure rate during the dry period was 83.94%. The cure rate for the major pathogens (98%) was significantly better (P < 0.05) than that for minor pathogens (78.9%). The overall quarter cure rate varied from 72.3% to 93.9% for the various products. The rate of new quarter infections during the dry period was 17.44% with a significant difference (P < 0.05), between the prevalence of new quarter infections with major (4.32%) and minor pathogens (13.12%). CNS was the most prevalent pathogen causing new quarter infections (12.34%) and the rate of new quarter infections varied from 13.4% to 24.1% for the various products. It is concluded that there is a difference in efficacy between antimicrobial intramammary dry-cow products in their ability to cure and prevent new IMIs during the dry period. Dry-cow products are mainly formulated for efficacy against Gram-positive cocci, while providing no or little protection against Gram-negative bacteria. Therapeutic levels may persist for only 14 to 28 days into the dry period and fail to protect the udder during the last trimester. Dry-cow therapy should, however, always form part of a holistic approach to the dry period which also considers cow factors, dry-cow management, microorganisms and the environment of the dry cow.
Highlights
Mastitis is a multi-factorial disease and generally results from an interaction between a variety of microbial infections, host factors, environment and manageaDepartment of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa.Received: December 2004
To eliminate mainly existing intramammary infections (IMIs) and in preventing new IMIs, blanket anti-microbial intra-mammary dry-cow therapy remains a fundamental part of a successful mastitis control programme[14,45]
The overall cure rate of IMI observed during the dry period was high, as well as the cure rate for IMI with major pathogens
Summary
Mastitis is a multi-factorial disease and generally results from an interaction between a variety of microbial infections, host factors, environment and manageaDepartment of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa.Received: December 2004. Mastitis is a multi-factorial disease and generally results from an interaction between a variety of microbial infections, host factors, environment and manageaDepartment of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa. The importance of the dry period with respect to udder health, productivity, overall health and fertility performance in the lactation has been widely documented[14,16,25,31,32,54]. The dry period is a period of anatomical, physiological and metabolic change for many body systems, including the mammary gland. The risk of mastitis depends on how well the defence mechanism of the dairy cow can adjust to the challenge as well as the risk from the environment and the microbes
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