Disclaimer: Whilst Neotest’s diagnostic tools for antibiotic residue testing are developed in line with rigorous scientific, veterinary, and regulatory standards, this article is intended for general understanding only. It should not be relied upon as veterinary or scientific advice. For critical decisions, always consult a qualified expert.
Somatic cell count (SCC) is commonly used to assess udder health and milk quality, but the number only becomes useful when its context is clear. A result around 200,000 cells/mL may be used to screen an individual cow for possible intramammary infection, while figures such as 400,000 or 750,000 cells/mL can appear in regulatory milk criteria.
These are not competing definitions of “normal SCC.” They answer different questions.
Somatic cells in cow’s milk are predominantly immune cells, particularly leukocytes, together with mammary epithelial cells. Their numbers commonly increase during mammary inflammation, which is why SCC is useful for mastitis screening and monitoring. It is normally reported as cells per millilitre. (Source: Li et al. (2014), Role of somatic cells on dairy processes and products: a review — PMC full text)
Before interpreting any result, check four things:
- Sample type: individual cow, quarter or bulk milk.
- Purpose: infection screening, herd monitoring, milk-buyer specification or regulatory control.
- Pattern: isolated result, sudden increase or persistent elevation.
- Context: sampling time, lactation stage and the animal’s recent history.
SCC Thresholds: Why 200,000, 400,000 and 750,000 Mean Different Things
One of the easiest SCC mistakes is to compare numbers that were created for different decisions.
| SCC value | Main context | What it can mean | What it does not mean |
|---|---|---|---|
| Around 200,000 cells/mL | Cow-level udder-health screening | Increased likelihood of intramammary infection and a reason for closer investigation | Proof that infection is present or a universal legal limit |
| ≤400,000 cells/mL | EU raw cow’s milk criterion | Rolling geometric average over three months, normally based on at least one sample per month | Universal individual-cow mastitis threshold or a single-sample definition of safe/unsafe milk |
| ≤750,000 cells/mL | U.S. Grade “A” individual producer milk | Regulatory SCC maximum under the 2025 Grade “A” PMO | An optimal herd-health target or evidence that every cow below it is uninfected |
Current EU legislation retains the ≤400,000 cells/mL raw cow’s milk criterion as a rolling three-month geometric average. (Source: Regulation (EC) No 853/2004, current consolidated EUR-Lex version — EUR-Lex regulation). The 2025 U.S. Grade “A” PMO instead states that individual producer milk must not exceed 750,000 cells/mL. (Source: U.S. FDA, Grade “A” Pasteurized Milk Ordinance, 2025 Revision — FDA 2025 PMO PDF; FDA document page — NCIMS Model Documents)
The approximately 200,000 cells/mL figure has a different purpose. It is widely used as a screening threshold for intramammary infection, but screening is not diagnosis. In published cow-level research, a 200,000 cells/mL threshold produced sensitivity of 65.1% and specificity of 73.0% for major-pathogen intramammary infection. That means some infected cows fell below the threshold and some uninfected cows exceeded it. (Source: Jashari et al. (2016), Evaluation of the composite milk somatic cell count as a predictor of intramammary infection in dairy cattle, Journal of Dairy Science — Journal of Dairy Science full text)
The practical lesson is simple: a biological screening threshold, a commercial trigger and a regulatory milk criterion should not be interpreted as the same type of number.
Somatic Cell Count in Milk: Individual Cow SCC vs Bulk Milk SCC
Individual and bulk SCC are complementary, not interchangeable.
| Measurement | Main question | Best use | Main limitation |
| Individual cow or quarter SCC | Which cow or quarter may have increased mammary inflammation? | Screening animals, reviewing repeated results and prioritising further investigation | Does not identify the pathogen by itself |
| Bulk milk SCC | What is happening to SCC across the herd or milk supply? | Monitoring herd-level trends and milk-quality performance | Cannot identify which animal is responsible |
A rising bulk SCC tells you that the aggregate situation has changed. It does not identify the source. Moving from a bulk signal to individual-cow data is therefore often the next analytical step.
Why a Single SCC Result Can Mislead
SCC is associated strongly with mammary inflammation, but the measured value is also affected by biological and sampling conditions. Lactation stage, parity, production level and environmental or management factors can influence observed SCC. (Source: Alhussien & Dang (2018), Milk somatic cells, factors influencing their release, future prospects, and practical utility in dairy animals: An overview — PMC full text)
Look for patterns, not only cutoffs
A repeated sequence can distinguish situations that one measurement cannot:
- consistently low SCC;
- a sudden increase from the cow’s previous baseline;
- persistently elevated SCC;
- repeated movement between lower and higher results.
For this reason, historical SCC data generally provide more decision value than an isolated number.
Sampling relative to milking matters
A controlled study taking quarter samples before, during and after milking found marked changes in the diagnostic performance of SCC thresholds across the milking interval. At a 200,000 cells/mL cutoff for major-pathogen infection, specificity fell substantially after milking before gradually increasing again. The authors therefore highlighted premilking sampling when SCC is being interpreted for intramammary infection status. (Source: Olde Riekerink et al. (2007), Somatic Cell Count During and Between Milkings, Journal of Dairy Science — Journal of Dairy Science article / PubMed record)
This is more useful than assuming that “morning SCC” or “afternoon SCC” is always inherently higher. A consistent sampling protocol and the time relative to milking are more important interpretive details.
What SCC Can Tell You — and When You Need a Different Test
SCC is primarily an indicator of the cellular inflammatory response occurring in milk. It cannot answer every milk-quality question.
| Measurement or test | Main question answered | Important limitation |
| Somatic cell count | Is there an increased cellular/inflammatory signal consistent with poorer udder health? | Does not identify a specific pathogen or antibiotic residue |
| Bacterial/plate count | What bacterial load is present under the specified test conditions? | Measures a different milk-quality parameter from SCC |
| Culture or PCR | Is a particular microorganism present? | Does not replace SCC trend monitoring |
| Antibiotic-residue screening | Are target veterinary-drug residues detectable under the test’s conditions? | Does not measure SCC or diagnose mastitis |
This distinction is reflected in milk regulation itself. EU rules list SCC and plate count as separate raw-milk criteria and separately address antibiotic residues. (Source: Regulation (EC) No 853/2004 — EUR-Lex regulation)
It becomes especially important after antibiotic treatment for mastitis. A low SCC does not demonstrate that treated milk is free from antibiotic residues. EU rules require animals receiving treatments capable of transferring residues into milk to be identified and milk obtained before the prescribed withdrawal period has ended not to be used for human consumption. (Source: Regulation (EC) No 853/2004, Annex III, Section IX — EUR-Lex regulation)
Where residue screening forms part of the applicable control programme, a residue-specific test is required. Neotest offers rapid milk tests for antibiotic residues, including multi-residue formats. These tests answer a different question from SCC measurement and should be used according to their intended purpose and the relevant food-safety or residue-control procedure.
Where antibiotic-residue screening is required, Neotest provides rapid strip tests for milk designed to detect antibiotic residues, including β-lactams, streptomycin, chloramphenicol and tetracycline. *This is a separate control step from SCC measurement: the two tests answer different milk-safety questions.
What High SCC Can Mean for Milk Yield and Processing
Elevated SCC matters beyond identifying animals that may require investigation.
In one research dataset, cows with SCC around 250,000 cells/mL produced an average 1.6 kg less milk per day than cows at approximately 50,000 cells/mL. The same study also found lower feed efficiency with increasing SCC. This is evidence of an economic relationship, not a universal loss formula for every herd. (Source: Potter, Arndt & Hristov (2018), Increased somatic cell count is associated with milk loss and reduced feed efficiency in lactating dairy cows, Journal of Dairy Science — PubMed record)
SCC can also matter to processors. A review of dairy-processing research warns that the effect of somatic cells cannot always be separated cleanly from inflammation, bacterial status and accompanying changes in milk composition, so simple cause-and-effect claims should be treated cautiously. (Source: Li et al. (2014), Role of somatic cells on dairy processes and products: a review — PMC full text)
A two-year Parmigiano Reggiano study provides a useful process-specific example. In ten paired cheesemaking trials, milk in the higher-SCC group of 400,000–1,000,000 cells/mL had greater fat losses during cheesemaking and produced 8.79% lower cheese yield after 24 months of ripening than the lower-SCC group. That result applies to the specific production system studied and should not be transferred directly to every cheese or dairy process. (Source: Franceschi et al. (2020), Quantification of Cheese Yield Reduction in Manufacturing Parmigiano Reggiano from Milk with Non-Compliant Somatic Cells Count, Foods — PMC full text)
Somatic Cell Count in Milk: What to Check When SCC Rises
An elevated SCC should trigger a structured investigation rather than an automatic conclusion.
- Confirm what was sampled. Determine whether the result represents a quarter, an individual cow or bulk milk.
- Compare it with previous measurements. Decide whether the result is new, persistent or part of a fluctuating pattern.
- Check sampling context. Consider sampling relative to milking, lactation stage and recent calving.
- Move from bulk to individual data where necessary. A bulk-tank rise identifies a herd-level change, not the contributing animal.
- Use appropriate diagnostic investigation when the cause matters. SCC alone cannot identify the responsible pathogen.
- Treat residue control as a separate question after veterinary-drug use. Follow the prescribed withdrawal period and applicable residue-control procedures rather than using SCC as evidence of residue status.
The most useful interpretation of SCC is therefore not simply “Is this number high?” It is “What does this number mean for this sample, in this context, and what question needs to be answered next?”
This article is informational. SCC interpretation, mastitis diagnosis, veterinary treatment, residue control and milk-acceptance requirements may vary by animal, testing programme, jurisdiction and milk-supply contract.
