5 Must-Know Facts About Somatic Cell Count
Somatic cells in milk are one of the most important windows into udder health, milk quality, and dairy profitability, and managing somatic cell count (SCC) is central to making high-quality dairy products.
Somatic cells are mainly white blood cells and a smaller number of udder lining cells that naturally end up in milk. At low levels they are a normal part of milk and help protect the udder, but rising SCC usually signals the immune system is fighting an intramammary infection such as mastitis.
· In a healthy cow, SCC is typically under about 100,000 cells/mL, and many high-performing herds average well below 200,000 cells/mL.
· As bacteria invade through the teat canal and cause mastitis, leukocytes flood into the udder, driving SCC higher in individual quarters and in the bulk tank.
SCC links cow health, milk quality, and economics in a direct line.
· High SCC indicates more mastitis, which reduces milk yield, damages udder tissue, and increases treatment and culling costs.
· Elevated SCC changes the composition of milk, hurting product quality, cheese yield, flavor, and shelf life, so many processors pay premiums for low-SCC milk and may reject loads above internal standards.
In the United States, the legal maximum bulk tank SCC for Grade A milk is 750,000 cells/mL, but national averages are much lower because processors and farms aim for counts under 200,000 cells/mL to maintain quality and premiums.
3. How SCC affects milk and dairy products
As SCC rises, milk behaves differently in the plant and in the consumer’s refrigerator.
· Major components such as fat, lactose, casein, and potassium tend to decrease at high SCC, while whey proteins, lactoferrin, sodium, and chloride increase, which can reduce cheese yield and alter processing performance.
· Enzymes released from inflammatory cells, including proteases and lipases, break down protein and fat, leading to off-flavors (rancid, bitter, salty) and shorter shelf life in fluid milk and manufactured products.
For cheese makers, high SCC milk often means lower casein content, slower or weaker coagulation, and more defects, so they have strong incentives to source low-SCC milk. For fluid milk and cultured products, elevated SCC raises the risk of inconsistent texture, stability problems, and consumer-detectable flavor defects.
Interpreting SCC correctly helps target decisions at the cow and herd level.
· Individual cows:
o Around 100,000 cells/mL or less is generally considered “uninfected.”
o Around 200,000 cells/mL is a common threshold where infection becomes likely, especially for subclinical mastitis.
o Well above 200,000 cells/mL suggests at least one quarter is infected and needs attention.
· Bulk tank:
o Many herds now treat a bulk tank SCC at or above 200,000 cells/mL as a warning that subclinical mastitis is circulating in the herd.
o Research has shown that reducing SCC from about 600,000 to 200,000 cells/mL can recover hundreds of pounds of milk per cow per year and improve premiums.
Interestingly, very low SCC (for example, below about 50,000 cells/mL) is not always a guarantee of freedom from pathogens, and some very low-SCC samples still harbor bacteria, so SCC should be interpreted alongside culture or other diagnostics.
5. Tools to measure and lower SCC
Modern dairies use SCC as a daily management tool rather than just a regulatory number.
· Measuring SCC:
o Lab-based methods like fluorescence flow cytometry or Coulter counting, used by DHI and processing plants, give accurate SCC down to about 10,000 cells/mL.
o On-farm tests like the California Mastitis Test (CMT) or portable SCC analyzers help pinpoint high-SCC quarters cow-side, especially for subclinical mastitis.
· Managing and lowering SCC:
o Mastitis control basics—clean, dry bedding; effective pre- and postmilking teat disinfection; proper milking routines and equipment maintenance; and blanket or selective dry-cow therapy—remain the backbone of SCC reduction.
o Strategic culling of chronic high-SCC cows that fail treatment can rapidly lower bulk tank SCC in a small percentage of the herd.
o Good nutrition, including adequate energy and key micronutrients such as selenium and vitamin E, supports immune function and resistance to udder infections.
Research on feed additives also shows promise: a phytobiotics-rich herbal mixture (rosemary, cinnamon, turmeric, clove) decreased somatic cell score, improved milk yield, and enhanced udder health in cows that started with high SCC, suggesting that targeted antioxidant and anti-inflammatory supplements can complement traditional mastitis control.
For consumers, the practical takeaway is simple: milk from herds with low somatic cell counts typically comes from healthier cows, has better processing performance, and offers more consistent flavor and shelf life, even though all Grade A milk meets basic safety standards.
Sources:
1. https://somaticcellcounttester.com/10-must-know-facts-about-somatic-cell-count/
2. https://vet.osu.edu/sites/default/files/documents/da-costa-rovai_low-somatic-cell-count_v7-final.pdf
3. https://extension.psu.edu/milk-quality-effects-of-a-high-somatic-cell-count/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC5993762/
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8. https://fieldreport.caes.uga.edu/publications/B1194/somatic-cell-count-benchmarks/
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