Controlling mastitis is critically important for dairy profitability and producing high quality milk. A long-standing recommendation to achieve this goal is that all cows, and all quarters of the udder be treated with an antimicrobial at dry-off time. Is this practice still important?
In a three-part series of articles from Michigan State University Extension, we will explore the reasons to reconsider blanket dry cow treatment, the research on selective treatment and then put what we know into practice for dairy producers.
In a 2013 survey of herds in Michigan, Pennsylvania and Florida conducted by the Quality Milk Alliance project led by Dr. Ron Erskine of Michigan State University, 75 percent of all herd owners (n=628) reported they always use dry cow treatment on cows and another 16 percent use it either often or sometimes. In this study, use of dry cow treatment was associated with lower herd somatic cell counts (SCC).
Dry treatment consists of an antimicrobial that is formulated to provide an effective therapeutic level for an extended period of time. The use of dry treatment has been shown to provide a better cure rate of some types of mastitis than lactation antimicrobial therapy and it also serves to protect the udder from infection through the dry period, especially during in the early weeks after dry-off.
One of the reasons that we always said “every cow, every quarter” was because we didn’t know which cows and quarters might have a subclinical infection that was not readily apparent. Therefore, the most prudent thing to do was to treat all. But the landscape has changed.
The specific organisms causing infections on farms have changed. It used to be that the contagious organisms, Strep. agalactiai and to a lesser extent, Staph. aureus were more common in herds and the somatic cell counts of herds were higher, indicating more infected quarters in the herd.
Today, many producers have eliminated those contagious organisms from their herds. In many dairies, the primary organisms causing mastitis are environmental Streptococci and Coagulase-negative Staphyolocci (CNS). In addition, herd SCC’s are significantly lower, a direct result of better udder management during milking. Additionally, teat sealants have reduced the opportunity for new infections associated with dry-off. The fact that subclinical infections at dry-off are less common may make blanket treatment of all cows and all quarters overkill.
In fact, unless excellent practices are used in preparing teats for antimicrobial infusion, we may actually cause infections by moving bacteria at the teat end into the teat canal. These are all good reasons to reconsider blanket dry cow treatment.