High somatic cell count in milk most often results from udder infections such as mastitis, leading to a noticeable decline in milk quality and market value. Dairy cows with elevated somatic cell count produce less milk and experience higher health risks. The somatic cell count tester allows farmers to monitor udder health and quickly identify the causes of high somatic cell count in milk. Controlling somatic cell count supports animal well-being and maintains dairy profitability.
Key Takeaways
- High somatic cell count mainly comes from udder infections like mastitis, which lowers milk quality and yield.
- Regular testing with a somatic cell count tester helps farmers find problems early and keep cows healthy.
- Good farm management, clean milking practices, and proper cow nutrition reduce the risk of high somatic cell count.
- Heat stress and poor housing increase somatic cell count in milk by weakening cows’ immune systems.
- Lowering somatic cell count improves milk taste, processing quality, and farm profits.
Somatic Cell Count
What Are Somatic Cells?
Somatic cells are mainly white blood cells and a small number of epithelial cells found in milk. These cells enter the milk from the udder tissue, especially when the udder faces stress or infection. In healthy dairy cows, milk somatic cell counts remain low. When the udder becomes inflamed, as in mastitis, the body sends more white blood cells to fight infection, causing a high somatic cell count. Monitoring milk somatic cell counts helps identify udder health problems early.
Why SCC Matters?
Somatic cell count serves as a key indicator of udder health and milk quality. High somatic cell count signals inflammation, often from subclinical mastitis, which can go unnoticed without testing. When milk somatic cell counts rise, milk quality drops. Producers see lower fat, protein, and casein levels, which affects cheese yield and nutrient value. Maintaining low somatic cell count benefits dairy cows by reducing disease risk and supports better milk quality for consumers. Industry benchmarks set the upper limit for bulk milk somatic cell counts at 400,000 cells/mL in many countries. Monthly individual thresholds of 200,000 cells/mL help identify infected cows and maintain herd health.
Note: Regular monitoring of milk somatic cell counts protects both animal health and product value.
Measuring SCC
Modern technology allows accurate and efficient measurement of milk somatic cell counts. The somatic cell count tester uses advanced methods like fluorescence photoelectric detection and flow cytometry. These tools provide rapid, automated results with high sensitivity. The table below compares common methods for measuring somatic cell count in milk:
| Method Category | Specific Method | Applicability | Advantages | Disadvantages |
|---|---|---|---|---|
| Direct Detection | Fluorescence photoelectric | Enumeration method | Rapid, efficient, high reproducibility | Expensive, requires calibration and expertise |
| Direct Detection | Coulter counting | Enumeration method | Rapid detection | Complex sample pretreatment |
| Direct Detection | Flow cytometry | Enumeration method | Straightforward, efficient | High cost |
| Indirect Detection | California Mastitis Test | Screening method | Low cost, easy to operate | Only relative quantification, subjective |
| Indirect Detection | ATP bioluminescence | Screening method | Simple, rapid detection | Low accuracy, bacterial interference |
| Indirect Detection | Conductivity and pH | Screening method | Simple detection process | Lacks accuracy, requires microscopy for accuracy |
Somatic cell count test kit offers higher accuracy, faster results, and lower maintenance costs than traditional microscopic counting. These devices require only a small milk sample and can detect a wide range of cell concentrations. Dairy farmers use these testers to monitor milk somatic cell counts regularly, ensuring milk quality and herd health.
Causes of High Somatic Cell Count in Milk
Mastitis and Infections
Mastitis stands as the leading cause of high somatic cell count in milk. This udder infection occurs when bacteria invade the mammary gland, triggering an immune response. The body sends white blood cells to fight the infection, which increases milk somatic cell counts. Clinical mastitis presents with visible symptoms such as swelling, redness, and abnormal milk, while subclinical mastitis shows no obvious signs but still elevates somatic cell count. Both forms reduce milk quality and yield.
The most common pathogens responsible for clinical mastitis include Streptococcus and Staphylococcus species. These bacteria dominate the milk microbiome during infection, accounting for over 80% of cases. Subclinical mastitis often involves a rise in Streptococcus abundance, although the correlation with somatic cell count is weaker. Healthy cows show much lower levels of these pathogens.
| Clinical Group | Dominant Pathogens (Relative Abundance) | Notes on SCC and Pathogen Abundance |
|---|---|---|
| Clinical Mastitis (CM) | Streptococcus and Staphylococcus species (82% combined) | These two genera dominate milk microbiome in mastitis cases. |
| CM samples (median) | Streptococcal + Staphylococcal species (89.9%) | High combined median relative abundance in CM milk samples. |
| Subclinical Mastitis (SCC ≥250,000 cells/mL) | Increased Streptococcus genus abundance (cautiously interpreted) | Streptococcus abundance rises with SCC but correlation is weak. |
| Healthy (H) | Lower combined Streptococcus/Staphylococcus (45%) | Lower pathogen abundance compared to mastitis groups. |
| Other genera | Serratia, Pseudomonas, Yersinia (lower or unclear association) | Less prominent in mastitis-related elevated SCC samples. |
Clinical mastitis and subclinical mastitis both increase the risk of high somatic cell count in milk. Multiparous dairy cows face a higher risk of subclinical mastitis, especially after 305 days in milk. Milking frequency also plays a role. Cows milked three times per day have a lower risk of subclinical mastitis than those milked twice daily. High milk yield reduces the risk of subclinical mastitis, while contagious mastitis spreads easily within herds, further raising somatic cell count.
Management and Hygiene
Management and hygiene practices on dairy farms directly affect the causes of high somatic cell count in milk. Poor hygiene during milking, dirty equipment, and inadequate cleaning routines allow bacteria to enter the udder, increasing the risk of mastitis. Inefficient management techniques, such as skipping regular cleaning of milking lines or failing to use a somatic cell count tester, lead to higher milk somatic cell counts and reduced milk quality.
Key management factors include:
- Regular cleaning of milking equipment and lines
- Performing strip cup and California mastitis tests
- Washing teats with water before milking
- Implementing proper milking protocols
Only a small percentage of farmers use the full set of recommended management techniques, leaving many herds at risk for high somatic cell count in milk.
Poor milking protocols and inadequate cow comfort also contribute to elevated somatic cell count. Observational studies show that herds with high bulk tank somatic cell count often violate animal welfare standards. Cows with poor mobility or lameness experience higher somatic cell count and lower milk production. Milking protocols that use low milk flow rate switch-points can cause teat congestion, further increasing somatic cell count. Improving cow comfort and following best milking practices help reduce the risk of clinical mastitis and subclinical mastitis.
Nutrition and Stress
Nutrition plays a crucial role in the causes of high somatic cell count in milk. Dairy cows need balanced diets to maintain strong immune systems and healthy mammary glands. Nutritional deficiencies, such as energy shortages, unbalanced energy-to-protein ratios, or lack of essential vitamins and minerals, make cows more susceptible to mastitis. Metabolic disorders like subacute acidosis or ketosis, often caused by improper diets, increase the risk of clinical mastitis and subclinical mastitis.
- Supplementing diets with antioxidant vitamins (A and E) and minerals (selenium, zinc, copper) protects mammary cells and supports recovery from mastitis.
- Proper nutrition improves immune defenses, helping control somatic cell count score and maintain milk quality.
- High somatic cell count in milk reduces milk yield, alters composition, and lowers feed efficiency.
Physiological stress also raises somatic cell count in dairy cows. Stressful events, such as transport, cause a sharp increase in cortisol levels. This hormone surge releases more neutrophils into the bloodstream but prevents them from reaching tissues, leading to higher leukocyte and neutrophil counts in blood and milk. The neutrophil:lymphocyte ratio serves as a stress indicator. Stress-induced immune changes trigger inflammation in the mammary gland, increasing somatic cell count and the risk of mastitis.
Environmental and Physiological Factors
Environmental and physiological factors represent additional causes of high somatic cell count in milk. Housing conditions, climate, and heat stress all influence the health of dairy cows and the risk of mastitis. Studies show that heat stress, measured by the temperature-humidity index (THI), raises somatic cell scores in milk, especially during summer months. Warm housing systems and high THI values correlate with increased somatic cell count and changes in milk production traits.
- Heat stress weakens the immune response, making cows more vulnerable to mastitis.
- Activation of the hypothalamic–pituitary axis during heat stress reduces thyroid hormones, slowing metabolism and decreasing feed intake.
- Vasodilation increases energy expenditure and reduces overall health.
- Warm, humid conditions increase environmental pathogen loads, especially coliform bacteria, raising the risk of clinical mastitis and subclinical mastitis.
- Somatic cell score rises with higher THI and diurnal temperature variation, serving as an early indicator of heat stress.
Other physiological factors, such as stage of lactation and parity, also affect the risk of mastitis and high somatic cell count in milk. Multiparous cows and those in late lactation face greater risk. Using a somatic cell count tester helps farmers monitor these factors and take timely action to protect herd health.
Dairy farmers who address all these factors—mastitis, management, nutrition, stress, and environment—can better control the causes of high somatic cell count in milk and maintain optimal milk quality.
Impact on Milk Quality
Changes in Composition
High somatic cell count causes significant changes in milk composition. These changes result from inflammation in the mammary gland, which alters the permeability of udder tissue and affects the transfer of nutrients into milk. Scientific studies have identified several key shifts in milk components:
- Milk yield decreases as somatic cell count rises, with losses reaching up to 12% overall and nearly 17% in cows during their second lactation.
- Lactose content drops significantly, which signals damage to the mammary gland and reduced milk quality.
- Protein, fat, and total solids increase as somatic cell count rises. For example, milk fat can rise from 3.65% to 3.92%, and protein from 2.94% to 3.11% as somatic cell count increases from ≤200 to ≥1000 ×10³ cells/mL.
- No significant change occurs in milk urea nitrogen.
- The increase in protein and fat does not reflect improved milk quality. Instead, it results from the leakage of blood proteins and fat due to inflammation.
In addition to these changes, enzyme activity in milk also shifts with high somatic cell count:
- Endogenous enzymes such as cathepsin D, cathepsin B, elastase, and lipoprotein lipase increase in activity.
- These enzymes mainly come from white blood cells, especially neutrophils and macrophages, which flood the udder during infection.
- Elastase and lipoprotein lipase activities rise sharply, leading to more rapid breakdown of milk proteins and fats.
- Plasmin activity, which breaks down casein, also increases with somatic cell count.
These compositional and enzymatic changes lower milk quality and make it less suitable for processing into high-value dairy products. Farmers who use a somatic cell count tester can detect these changes early and take action to protect milk quality.
Sensory and Processing Effects
High somatic cell count not only alters the composition of milk but also affects its taste, odor, shelf life, and processing characteristics. These effects become clear during storage and dairy product manufacturing.
- Increased enzyme activity in high somatic cell count milk leads to greater lipolysis and proteolysis. This means fats and proteins break down faster.
- As a result, milk develops off-flavors such as rancidity and bitterness, especially after 14 to 21 days of refrigeration.
- These sensory defects appear even when microbial counts remain low, showing that biochemical changes—not spoilage bacteria—cause the decline in milk quality.
- Milk with low somatic cell count maintains good taste and odor throughout its shelf life, while high somatic cell count milk loses quality much sooner.
Processing high somatic cell count milk into cheese or other dairy products presents further challenges. The increased activity of proteolytic and lipolytic enzymes degrades casein and fat, which are essential for curd formation. This leads to:
- Poorer coagulation properties and weaker curd firmness.
- Lower cheese yield and reduced efficiency in dairy processing.
- Introduction of compounds from udder infections that further harm dairy product quality.
Dairy processors rely on high milk quality to achieve optimal cheese yield and product consistency. Using a somatic cell count tester helps identify milk that may cause processing problems before it enters the production line.
Economic Impact
The economic consequences of high somatic cell count in milk are substantial for both individual farmers and the dairy industry. Financial losses arise from reduced milk yield, lower product value, and penalties for poor milk quality.
Research shows that:
- Daily milk value losses per cow range from about $1.20 in the first month of elevated somatic cell count (≥100,000 cells/mL) to $2.06 by the tenth month.
- These losses increase with the duration of high somatic cell count, reflecting the impact of chronic mastitis on both milk yield and quality.
- Large-scale studies confirm that milk loss varies by herd and cow parity, but the per cow loss remains a reliable measure for estimating financial impact.
- Farms with persistently high somatic cell count face reduced income from milk sales, lower bonuses for quality, and higher costs for veterinary care and management interventions.
A table summarizing the economic impact:
| Duration of High SCC | Estimated Daily Loss per Cow | Main Causes of Loss |
|---|---|---|
| 1st Month | $1.20 | Lower yield, reduced quality |
| 10th Month | $2.06 | Chronic mastitis, penalties |
Maintaining low somatic cell count with regular use of a somatic cell count tester protects milk quality and supports economic sustainability for dairy farms.
High milk quality benefits everyone in the supply chain, from farmers to processors to consumers. Preventing elevated somatic cell count ensures better dairy product quality and long-term profitability.
Reducing High Somatic Cell Count
Monitoring and Testing
Effective control of somatic cell count begins with regular monitoring. Farmers use a somatic cell count tester to check individual cows and the bulk tank SCC. Automated on-farm sensors, such as the online California Mastitis Test, allow for daily or even per-milking measurements. This frequent testing helps detect mastitis early and track changes in udder health. Repeated measurements, combined with bacterial culture and qPCR, confirm infections and guide treatment. Bulk milk somatic cell count and total bacterial count serve as herd-level indicators of milk quality. Adjusting SCC thresholds based on cow parity and lactation stage improves detection, especially for Staphylococcus aureus. Proper sampling, including aseptic collection before milking, ensures accurate results.
Tip: Daily monitoring with a somatic cell count tester enables early intervention and supports high milk quality.
Udder Health and Hygiene
Maintaining udder health and hygiene is essential for reducing mastitis and improving milk quality. Farmers should clean teats before and after milking, using paper towels for best results. Studies show that this practice lowers the risk of mastitis and helps achieve lower somatic cell counts. Properly functioning milking machines prevent teat injuries, which can otherwise increase infection risk. Clean bedding, especially around calving, reduces environmental pathogens that cause mastitis. Routine use of the somatic cell count tester helps identify cows needing extra care.
Management Strategies
Management strategies play a key role in lowering somatic cell count. Selective dry cow therapy stands out as an effective approach. Farmers treat only cows with existing infections at dry-off, based on SCC and mastitis records, while using teat sealants for all cows. This method reduces antibiotic use and prevents new infections. Selective dry cow therapy requires accurate milk recording and timely treatment. Comfortable housing, deep bedding, and cooling systems improve cow comfort and reduce mastitis risk. Nutritional supplements, such as zinc and selenium, support immune function and help maintain milk quality. Selective dry cow therapy, combined with good nutrition and hygiene, leads to healthier cows and better milk quality.
Note: Selective dry cow therapy, when used with regular monitoring and proper hygiene, offers a sustainable way to achieve lower somatic cell counts and protect milk quality.
Conclusion
High somatic cell count in milk results mainly from mastitis, poor management, and environmental stress. These factors lower milk quality and farm profits. Regular use of a somatic cell count tester supports early detection and better herd health.
- Early monitoring helps reduce mastitis risk and supports higher milk yield.
- Tailored protocols and genomic tools improve herd longevity and profitability.
- Lower somatic cell count leads to better reproductive performance and reduced costs.
| Statistic/Comparison | Key Findings |
|---|---|
| Median herd SCC by area | Area A: 164,000 cells/mL; Area B: 211,000 cells/mL; Area C: 161,000 cells/mL |
| Correlation between herd SCC and CSM morbidity | Strong positive correlation, r = 0.9093 |
Many producers believe high somatic cell count always means poor milk safety, but it mainly signals udder infection, not pathogens. No visual test can guarantee milk quality or safety.
Dairy farms that focus on proactive management and regular testing maintain low somatic cell count, ensuring high milk quality and long-term profitability.
FAQ
What Is a Somatic Cell Count Tester?
A somatic cell count tester is a device that measures the number of somatic cells in milk. Farmers use it to check udder health and detect mastitis early. This tool helps maintain milk quality and supports herd management.
How Often Should Farmers Test Milk for Somatic Cell Count?
Farmers should test milk at least once a month. Many use a somatic cell count tester more frequently, especially after noticing changes in milk yield or quality. Regular testing helps catch problems early and improves herd health.
Can High Somatic Cell Count Affect Cheese Production?
Yes, high somatic cell count can lower cheese yield and weaken curd formation. Enzymes from infected milk break down proteins and fats, making cheese production less efficient. Dairy processors prefer milk with low somatic cell counts for better results.
What Steps Help Lower Somatic Cell Count in Milk?
- Clean teats before and after milking
- Use a somatic cell count tester regularly
- Provide balanced nutrition
- Ensure cow comfort and proper housing
- Treat mastitis quickly
Tip: Consistent management and early detection keep somatic cell count low and milk quality high.