Mastitis Testing: CMT, Cell Count, Culture and RT-PCR

Mastitis testing works like a ladder. A cowside CMT shows which quarter of the udder is inflamed, a cell count measures how much, a culture finds the germ and shows which antibiotics may work, and RT-PCR finds germs that are hard to grow. Each step answers a different question, and a vet decides how far up the ladder to go.

Step 1: the cowside CMT

The California Mastitis Test (CMT) uses a small paddle with four cups. A little milk from each quarter is mixed with a reagent, and the mixture thickens if the milk holds many body cells. It takes a minute, needs no machine and can be done by the vet or a trained farmer at the cowside. It shows which quarters are affected and how strongly, even when the milk looks normal. It does not name the germ.

Step 2: the somatic cell count

Somatic cells are body cells, mostly white blood cells, that enter milk when the udder is inflamed. The Somatic Cell Count (SCC) - Milk counts them in the lab, so it gives a measurable picture of udder inflammation for one animal or for the whole herd's milk. The lab report shows the reference range, and the lab quotes no cut-off numbers. A rising count over several tests is a warning that vets take seriously.

Step 3: milk culture and sensitivity

The Milk Culture & Sensitivity (Mastitis) grows the germ from the milk on a dish and identifies it. The lab then tests which antibiotics affect it. This is the step that answers "what is causing this and what may work against it". The milk must be collected clean and, importantly, before any antibiotic is given, because medicine in the milk can stop the germ from growing and give a false negative. Your vet decides on treatment from the result, and the lab gives no treatment advice.

Step 4: RT-PCR for hard-to-grow germs

Some mastitis germs grow slowly or not at all on an ordinary dish, and some come and go in the milk. The Mastitis Pathogen RT-PCR Panel is an RT-PCR (real-time PCR) test that looks for the genetic material of several common mastitis germs. The exact list is confirmed when you book. RT-PCR is often used when mastitis keeps coming back, when culture is negative in an animal that is clearly inflamed, or when the herd has a puzzling pattern. The Mastitis Deep Check Pack groups the steps for animals with stubborn infections.

How should quarter samples be taken?

Good sampling decides the value of every step.

1. Wash and dry your hands, and wear clean gloves.
2. Clean and dry each teat, and wipe the tip with a clean cloth or swab.
3. Discard the first few streams.
4. Hold the sterile tube at an angle and collect milk without touching the rim to the teat.
5. Label each tube with the animal's number, the quarter and the date and time.
6. Keep the tubes cool and send them quickly.

Take quarter samples separately, because mastitis often affects one quarter only. Mixed milk from the whole herd can be used for a herd cell count.

What do the results mean for the herd?

A registered veterinarian reads the results with the animal's signs and history. A herd with many high counts may need a review of milking hygiene and housing. The lab confirms the sample needs and the reporting time when you book. Results are for your information, and do not replace official food-safety testing.

Read next

For older animals that need regular checks, read Older Dairy Cows and Buffaloes: Tests for Fertility and Longevity. For another aspect of herd care, see Pregnancy Diagnosis in Cows and Buffaloes: Progesterone and PSPB.

Testing in Bhopal

Your vet usually helps with milk samples, and the lab at C-200, C Sector, Shahpura, Bhopal accepts them. Collection is free anywhere in Bhopal, and other districts can send chilled milk by courier or through their vet. Call or WhatsApp +91 88175 01118; the lab confirms the method, sample needs and reporting time when you book.