Use of intramammary penecillin to treat mastitis
A recent study by M. Clews (based in Reporoa) looked into the treatment of spring mastitis on an individual case by case basis compared to using a certain product depending on days in milk (more of a herd level protocol). This herd level approach reflects the traditional practice of penicillin use in early lactation and cloxacillin use later on in lactation. The study was conducted across four locations in NZ. Every case of mastitis was cultured in clinic from a sample taken that day by the farmer, and treatment was initiated before culture results were available.
The study was separated into two groups – a ‘case by case’ (CBC) group and a ‘days in milk’ (DIM) group. In the DIM group, all cows calved <7 days were treated with 3 x 12 hourly penicillin (Intracillin 1000 MC). Cases after 7 days were given 5 x 24 hourly cloxacillin (Orbenin LA). This group also had cultures taken, but treatment was not changed depending on diagnosis, it was only based on DIM. In the CBC group, the initial treatment was intramammary penicillin (Intracillin 1000 MC). At 24 hours, a decision was made based on the culture result (i.e. on a case by case basis). If Strep uberis, Strep dysgalactiae or CNS were cultured no more treatment was given, assuming penicillin would be sufficient treatment. If Staph aureus was cultured, the course was extended but with 3 x 24 hourly treatments of combined penicillin and cloxacillin (Penclox 1200 Milking cow) at 24-hour intervals. Any other pathogens were removed from the trial and treated accordingly.
Strep uberis was cultured in 43% and Staph aureus in 15% of the 767 clinical cases. For comparison, our clinic cultured 48% Strep and 25% Staph last year.
There was a significant difference between cure rates for Staph aureus with the two different protocols. CBC had a 44% cure rate and DIM a 24% cure rate. This outcome was also achieved with less total daily antibiotic, and more green antibiotics (on the traffic light system).
Penicillin is considered a green antibiotic, whilst cloxacillin is considered amber. Within the study, penicillin produced significantly higher cure rates than cloxacillin for Strep uberis. Treatment with 3x Intracillin MC followed by 3x Penclox resulted in higher cure rates for Staph aureus than 5x Orbenin LA (47% compared to 21%).
SUMMARY
This study showed that culture-based individual cow decision-making with regard to mastitis treatments can result in better clinical outcomes – whilst also increasing the use of ‘green’ rather than ‘amber’ antibiotics and reducing the total days of antibiotic treatment. It should be noted that all of the above treatments were administered on twice daily milking farms (even using once a day products).
This study reinforces the message to take samples from mastitis cows (pre-treatment), especially if you’re having a run of mastitis, multiple cases in a cow, or non-responsive cases. Our in-clinic lab can run a sample and have an answer in a day (even quicker than culture), helping us to make informed decisions about your cows. It also highlights how well straight penicillin can work as an effective mastitis treatment on farm. Find out your farm’s mastitis bugs’ sensitivity to different antibiotics with a dairy antibiogram (see article) for a herd-level picture, or send in a mastitis sample for a cow-level picture.
Dairy Antibiogram
Following on from the penicillin study, this article summarises the new additions in testing with the dairy antibiogram (DAB). Multiple farms in our clinic will run DABs again this season on bulk milk tank samples. The mastitis bacteria Strep uberis and Staph aureus from your farm are cultured and their sensitivity to a wide range of antibiotics is found. This is a herd level test specific to your farm, enabling decisions about which antibiotics to use for mastitis.
The tests already run sensitivity to six antibiotic families, including injectable penicillin, intra-mammary penicillin, intra-mammary cloxacillin, intra-mammary amoxicillin/clavulanic acid and tylosin.
Additional antibiotics now tested are lincocin and neomycin, oxytetracycline and cefuroxime. This means four new antibiotic families are being added, as well as new concentrations. This means more effective, responsible and sustainable mastitis treatments!