The Science Behind Better Somatic Cell Counts
The Science Behind Better Somatic Cell Counts
Somatic cell count (SCC) is a foundational pillar of milk quality. Herd average SCC is a good at-a-glance way to earmark overall herd health and milk management. Low counts don’t happen by accident. Rather, they are achieved with hard work and by making sure everyone involved in cow care and milk handling understands the basic science behind it.
SCC Basics
SCC is measurement of body cells and includes multiple cell types. According to the Agriculture and Horticulture Development Board, the majority of somatic cells are either leukocytes (white blood cells) or epithelial cells. Leukocytes are an immune response and increase in the milk as they fight off an udder infection. Epithelial cells, which make up a small percentage of somatic cells, are milk production cells that shed off within the udder during an infection.
SCC measures both overall cow and udder health plus the quality of your milk. It is worth noting that while somatic cells occur naturally even in healthy herds and pose no threat to human health, they are still an important metric. Beyond the ethics, processors often pay premiums for lower SCC milk, meaning this simple practice can add a premium to the bottom line. In healthy cows, low SCC levels are generally cited around or below ~100,000 cells/mL.
Causes and Environmental Factors
The major reason a farm wants to stay on top of SCC is that subclinical cases of mastitis can hijack this number even if only a “normal” percentage of cows are clinically infected.
Because the spectrum of bacteria and other pathogens that can cause subclinical infections is so broad, the best defense against this is overall hygiene in the parlor and barns plus general herd health.
Industry guidelines for teat dipping should be followed each and every milking. All milkers should be trained on how to do so and understand why it’s important. Proper protocol includes full coverage of the teat when it is dipped along with adequate time for pre-dip to disinfect before wiping. As well, milking equipment should be sanitized properly. Cows should be encouraged to stay on their feet long enough for the teat end to rebuild its natural keratin plug post-milking. Offering fresh feed and a clean water tank immediately after they return to the barn can help this.
It’s also noteworthy here that having poor inflation size and inflations in bad condition or poor quality can cause more harm than good by damaging the teat end and milk canal.
Bedding and Milking Factors
Clean bedding and milking are also important for keeping bacteria away from the udder. A growing body of research shows exactly how the environment impacts SCC and udder health.
A 2011 longitudinal study evaluating cow hygiene and milk SCC found that cows classified as cleaner had significantly lower SCC levels than dirty animals. Cows were evaluated on multiple points of their bodies in addition to the udders.
“Individual variation was observed in the hygiene of cows throughout the year, with the highest proportion of clean cows being observed in August and the lowest in January. In spite of this seasonal variation, approximately half (55.62%) of the cows displayed consistent cleanliness scores, with 45.86% of them remaining consistently clean (very clean or clean) and 9.76% remaining dirty (very dirty or dirty) over the course of the study. The very clean cows had the lowest SCLS [somatic cell linear scores], followed by the clean, dirty, and very dirty cows (no statistically significant differences were found between the latter two groups).”
In a Cornell Cooperative Extension blog, dairy educator Daniela Roland points out that research has also noted that general high levels of stress hormones in dairy cows interferes with the immune system’s ability to fight bacterial invaders. When cows become heat stressed, they are at a higher risk of picking up a pathogen that may cause mastitis.
Heat, humidity and crowded or poorly ventilated housing increase physiological stress, weaken immune defenses, and elevate SCC. Research also shows that heat stress and high moisture compromise cow behavior and immunity, leading to increased intramammary infection risk and higher SCC.
Manage Milking
Effective SCC management starts with mastitis prevention. It is no secret that herds with structured health programs focused on mastitis control programs that combine hygiene, cow monitoring and prompt treatment are the ones that maintain lower bulk tank SCC and experience fewer production losses.
Preventing infections is far more effective than treating them after SCC has already increased. This is largely because subclinical mastitis can persist unnoticed while quietly elevating somatic cells and reducing milk yield.
As mentioned, make sure all milkers are trained so they are thorough and consistent with standard milking procedures. Inconsistent routines, or simple procedural drifting, are a documented risk factor for increased SCC and direct mastitis transmission.
Solid practices include stripping and training milkers to detect visible, early mastitis signs. This also helps to stimulate milk letdown, shortening milking time and reducing liner slips that can force bacteria into the teat canal.
Make sure equipment is routinely checked and regularly sanitized. Poorly functioning equipment including worn liners, incorrect vacuum levels or irregular pulsation can damage teat ends, increasing inflammation and SCC even when pathogen levels are relatively low.
A 2020 systemic review in the Journal of Dairy Science from Sao Paulo State University highlighted the link between rough or over milking conditions and teat end hyperkeratosis, which creates a physical environment that allows bacteria to colonize more easily. Regular liner replacement, system testing, and wash cycle checks help ensure equipment supports udder health rather than compromising it.
Herd Management
The dry period is one of the most important windows for SCC control. Strategic dry cow therapy has been shown to eliminate existing infections and reduce new infections in early lactation, when SCC often spikes.
Selective dry cow therapy can be effective when paired with strong records and consistent monitoring. Cows with chronically high counts that fail to respond to treatment may require culling to protect herd health, as they often serve as reservoirs for contagious pathogens.
Diet can also play a role. Immunity is impacted by several macro and micro nutrients including Vitamin A, Vitamin E and trace minerals such as selenium and zinc. Cows in negative energy balance or mineral deficiency will have delayed or impaired immune responses to both clinical and subclinical infections.
Finally, routine SCC data from individual cows, bulk tank trends and herd health records should inform management decisions. Monitoring trends allows producers to identify problem groups and catch upward ticks before higher counts become a herd wide issue.
Low somatic cell counts are not the result of a single practice, but of integrated management. While getting lower counts is always a win, it’s important to remember that maintaining them takes effort. This is especially true when facing abnormal weather conditions, external animal stressors and even high employee turnover rates.
April 2026
By Jaclyn Krymowski for American Dairymen
