Which Dry Cow Should I Use?

Choosing the right Dry Cow

“Which dry cow should I use this year?” This is a common and seemingly simple question we are asked a lot around this time of year. Unfortunately, the answer is surprisingly complex!

Breaking this question down makes it a bit easier to work through.

Should I use a blanket dry cow strategy or a selective dry cow strategy?

This all depends on the predominant mastitis causing bacteria in your herd, the prevalence of clinical mastitis in your herd, whether you herd test or not and the BMCC.  If you are not sure - blanket dry cow and TeatSeal is the safest option.

The flow chart based on the current CountDown recommendations on the next page gives a good guide as to whether or not you should consider using selective dry cow therapy or blanket dry cow therapy.

Should I use a 600 mg or 500 mg cloxacillin dry cow tube?

The reason for using an antibiotic dry cow therapy is to cure existing sub clinical infections over the dry period.  The ability of a dry cow therapy to do this depends on two things. Firstly, the antibiotic sensitivity of the predominant mastitis causing bacteria in your herd.  You can only gather this information by either regularly doing milk cultures on mastitis cases throughout the season using the Mastaplex system. Secondly, the length of time the dry cow therapy persist in the udder at a concentration that will kill the bacteria. 

The sensitivity of a bacteria to an antibiotic  is measured by the MIC (minimum inhibitory concentration).  This is the minimum concentration the antibiotic needs to achieve in the udder to kill the bacteria. 

If you are using the Mastaplex on-farm milk culture system, you will have access to detailed data on MIC values for the various mastitis causing bacteria in your herd.  The MIC 50 and MIC 90 can be calculated - these are the minimum antibiotic concentrations that will kill 50 % and 90 % of the population of a mastitis causing bacteria in your herd. Data from a local herd showing the MIC 50 and 90 for Staph aureus and Strep uberis for cloxacillin is shown in table 1 below.

Figure 3. Antibiotic persistence and MIC 90 for Strep. uberis and Staph. aureus (data from a local South Gippsland Herd) for a  500 mg and a 600 mg cloxacillin dry cow product.

As can be seen from Figure 3, the MIC 90 (1 ug/ml) for Strep. uberis will be reached for about only 7 days with the 500 mg cloxacillin dry cow and 47 days with the 600 mg cloxacillin dry cow.  The MIC 90 (4.0 ug/ml) for Staph. aureus will be reached for only 4 days with the 500 mg cloxacillin dry cow and 35 days with the 600 mg dry cow. 

What about Cephalonium dry cow tubes?

Cephalonium is a first generation cephalosporin that is available for use at drying off and lasts in the udder for up to 8 weeks.  Trial work has shown that generally there is no difference in cure rate, new cases of mastitis, cell count or milk production when compared to a 600 mg cloxacillin dry cow.  However, the cephalonium dry cow has been shown to have a higher cure rate than a 600 mg cloxacillin dry cow when treating cows infected with a particular bacteria - Corynebacterium bovis - so if this bacteria is an issue in your herd, this product probably has a place in your dry cow program.

Autumn Dry Cow Bundling Offer 

Bundle up your TeatSeal and antibiotic dry cow purchase with vaccines and drenches at dry off and save.  For each vaccine or drench you purchase with your dry cow, you receive $0.05 off each tube of antibiotic dry cow and TeatSeal - to be eligible for this discount you must purchase an equivalent number of doses of vaccine or drench as dry cow and/or TeatSeal.  In addition, we are offering a range of  volume discounts of up to $0.35 per tube on all dry cow products and sealants.  Talk to one of our vets or receptionists for more information.