Udder Health Monitoring with Somatic Cell Counts

Somatic cell count, or SCC, is the most widely used measure of udder health on dairy farms. Read well, it shows problems early. Read poorly, it gets blamed for things it does not say.

Key points

SCC signals inflammation but not the cause, so follow up with cultures.
Use cow-level reports to find the few cows driving the bulk tank number.
Separate new infections from chronic ones and plan for each.
Routine milking hygiene and clean bedding lower counts more than any single product.
Check limits and premium rules with your milk buyer, not from memory.

What somatic cells are

Somatic cells are mostly white blood cells that move into the udder to fight infection, along with a few cells shed from udder tissue. A healthy quarter has a low count. When bacteria get in, the body sends many more cells, and the count climbs.

SCC does not tell you which bacteria are present or whether a cow is sick enough to need a vet. It tells you that inflammation is likely, so you can look closer.

Bulk tank versus individual cow counts

The bulk tank count comes from your milk buyer and reflects the whole herd. It is the number that affects milk quality premiums and regulatory limits, and your buyer or state agency can tell you what applies to you. Do not guess at limits. Ask.

Individual cow counts usually come from your DHI or herd testing service. They show which cows are driving the tank. In many herds a small share of cows contributes most of the problem, so cow-level data is where the work happens.

Many herds set a simple trigger, such as reviewing any cow whose count rises above a chosen level on two tests in a row. Ask your vet or DHI advisor what trigger fits your herd and your milk buyer's quality program.

How to read the reports

Look at three things: where the herd average sits, how many cows are above your chosen cutoff, and how counts move from one test to the next. A cow that was low last month and high this month is probably a new infection. A cow that stays high month after month is likely a chronic case.

Ask your DHI technician or vet to explain the cutoff used for each report and any linear score or similar measure. Terms differ between services.

New high-count cows point to infections acquired recently
Chronic high-count cows may be candidates for culling decisions with your vet
First-calf heifers with high counts suggest a problem before or around calving
Compare fresh cows with late-lactation cows

Reasons counts rise

Counts go up with new infections, but also with age, advancing lactation, stress, heat and poor teat condition. A sudden herd-wide jump can follow a change in milking routine, equipment trouble, wet bedding or a season shift.

Do not assume the cause. Walk through milking procedure, equipment maintenance, bedding management and dry cow practice with your vet or a milk quality specialist.

Steps that bring counts down

Prevention does most of the work. Consistent pre-milking teat prep, clean and dry teats, correct unit attachment, post-milking teat dip, regular equipment checks, clean bedding and good dry cow management all matter. Segregating known chronic cows and milking them last limits spread.

Culture milk from problem cows so you know which bacteria are involved. The organism often decides the control plan. Your vet or a milk quality lab can help with sampling and interpretation.

Heifers and first-lactation cows deserve a separate look. If many heifers calve with high counts, the cause may lie in heifer housing, fly control, or how they are handled before first calving, not in the milking parlor at all.

What to ask and what to record

Keep a monthly log of bulk tank count, share of cows above cutoff, clinical cases and culture results. Review it with your vet at least a few times a year.

Questions to bring to that meeting: which cows are chronic, which pens or ages are worst, whether milking routine matches the protocol, and whether equipment has been tested recently.

Share the numbers with everyone who milks. People care more about a goal they can see, and a simple chart on the parlor wall makes progress, or setbacks, easy to notice.

Which cows are new versus chronic cases
What organisms are showing up in cultures
Whether teat condition is getting worse
When the milking system was last evaluated

When to get help: Call your vet for cows with clinical mastitis, swollen quarters or signs of systemic illness, and ask your milk buyer or state agency about quality limits. Any treated cow's milk and meat must be held for the full withdrawal time on the label or set by the vet.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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