Treatment response in mastitis cases is not just a bug-drug interaction. The complexities of the cow’s immune status as well as her age can also have an effect. Older cattle have a greater risk of both subclinical and clinical mastitis, and poorer responses to treatment compared to younger cattle.
“The influence of the cow on response to treatment doesn’t seem to be well recognized probably because treatment records on many farms are incomplete,” says Pamela L. Ruegg, DVM, MPVM, Dipl. ABVP, University of Wisconsin, Madison.
“Veterinarians need to teach producers to check the history of cows before they begin treatment and devise treatment protocols that take into account the information that is available.
”For example, she says, bacteriological cure rates have been shown to decline with parity; perhaps longer duration therapy is appropriate for a cow experiencing her second clinical case or for an older cow with a history of two to three months of high SCC. “We also need to make sure that cows are not treated inappropriately. Cows with long histories of repeated clinical cases are not good candidates for treatment,” she says.
Training farmers to review mastitis records before treating is an important role of the herd veterinarian, Ruegg states. “It is very common for me to find cows that have been treated repeatedly and that have a history of chronically increased SCC, even over the course of a couple of lactations. If the SCC of a treated cow remains increased for months and the cow has recurrent mild cases of mastitis, it is very important to determine the pathogen and then make some hard decisions.”
Ruegg explains that these potential decisions include:
- Targeting treatment — right drug, right duration
- Drying off a quarter that has shown that is will not cure
- Culling the cow
- Making a no further treatment decision — simply deciding that future cases will be dealt with by milk discard only.
Read the full article “Refining Mastitis Treatment Decisions” in Bovine Veterinarian here.