Dairy heifers are often the forgotten animals on the farm until they calve. But, paying attention to their housing and hygiene during pregnancy can influence whether or not they may get mastitis before they ever have a calf. “Unfortunately, it’s still true that producers may have the perception that heifer mastitis is not a problem,” says Steve Nickerson, PhD,
The highest-risk period of time for heifers to be exposed to mastitis-causing bacteria is after puberty when glands start to develop and produce secretions, which will support growth of bacteria. Steve Oliver, PhD, Univer-sity of
When infection happens
It’s been shown that the prevalence of heifer mastitis is highest in the last trimester of pregnancy (Fox, 1995). There are several reasons this may happen. Seasonality may be a part of it. Oliver says infections are higher in summer, next highest in the spring, then in the fall and winter, respectively.
Single-calf housing that is frequently moved can help prevent early exposure to mastitis-causing pathogens.
Nickerson says warm weather that brings on flies and higher ambient temperatures along with humidity are conducive to bacterial growth in the environment and on heifers’ teat skin. “Also, pasturing heifers with older, infected cows may enhance cross infections, especially in warm seasons when flies can serve as vectors.”
Jim Brett, DVM,
Nickerson adds that many heifers -- sometimes greater than 50% -- can become infected at the same time. Brett notes that he has not seen an incidence rate over 10-15% in a group showing “clinical signs” at a common time, but there may be several subclinical cases that become clinical later. “This promotes the quandary: If you have a high clinical incidence, do you treat only the individuals or the whole group?” he asks.
Brett agrees that the most common time to find clinical mastitis is in springers and adds that the next most common time is pre-breeding (10-15 months), and, “at least we find them when they’re brought up for breeding, which is a neglected group.”
Heifers can be examined during a variety of growth phases and when herd management practices allow, such as during AI, pregnancy check or hoof trimming. Nickerson looks for abnormal appearance and consistency of secretion and occasionally hard, indurated quarters.
Coagulase-negative Staphylococcus (CNS) is the most prevalent organism in these third trimester mastitis cases. However, Staphylococcus aureus, E. coli and Streptococcus can also be found.
Culturing is not routinely done for heifer mastitis, mainly because of the expense. “It’s impossible to get owners to do it,” Brett says, “and since our clinical cure rate has been so good, they ask, ‘Is it really necessary to spend the money, and then what do we do differently as a result of identifying the organisms?’”
Steve Nickerson, PhD, says many producers don’t realize heifer mastitis can be a problem.