Mastitis Decision Tree
September 2022

Once a case of mastitis has been found, what to treat with becomes the next decision. The age of the animal and time of year will year will often help with the treatment decision plan.

In the spring, most cases of mastitis in a heifer, will be Strep uberis. The most appropriate treatment will then be a penicillin based product. Ideally you want to take a sample from the mastitis case before any treatment is given.

Take the sample in a sterile manner so that it doesn’t become cross contaminated with a bug from the environment. Clean the end of the teat with either meths and cotton wool or a teat cleaning swab from a sterile pack.

Hold the sample container slightly away from the udder of the cow so that dirt cannot drop into the container from the udder. Don’t try to overfill the mastitis sample container. 1 cm depth in bottom of container is sufficient. More squeezes from the teat into the container, increases the risk of contaminating the sample.

Identify the sample with a permanent marker pen, including the cow ID and which quarter. If not going to be sent away for culture straight away, it can be stored in the freezer until required. If treatment is initially unsuccessful, the pre-treatment sample can be cultured to identify the organism accurately.

Some farmers are now using an electronic device on their farms to identify mastitis organisms and receive advice on best treatment plan to use. These Mastatest machines take 24 hours from the sample being put into the machine to the result being given. The vet clinic also receives a copy of the test result via email once the test is completed.

If the mastitis case is only mild, in some cases no antibiotic treatment is given until the result received. Farmers are however giving a non-steroidal anti-inflammatory drug to help reduce inflammation. If the machine identifies a gram- negative organism, they may decide to not use any antibiotic , but to just continue with the anti-inflammatory. This leads to an overall reduction in antibiotic use, which leads to responsible use of antibiotics.

Within the last 12 months we have had some outbreaks of mastitis on a large scale, not caused by the commonly encountered mastitis organisms.

One herd has had a large number of cases of Serratia mastitis. This organism causes an increase in Bulk SCC, but not a large number of clinical cases. This organism is basically untreatable with antibiotics, so leads to large numbers of cows having to be culled. The problem on the farm becomes managing Bulk SCC to prevent grading.

Another herd has recently had a large number of cases of Prototheca mastitis. This is caused by an algae, so again cannot be treated with antibiotics. Culling of identified cases unfortunately becomes the treatment plan.