Managing somatic cell count

Somatic cell count (SCC) increases when a cow’s udder is fighting infection, so it is a useful indicator of mastitis, both clinical and in particular the type you can’t see, subclinical mastitis. Higher SCC usually means infection and inflammation is present in the udder.

Regular measurement of bulk milk somatic cell count (BMSCC) acts as a herd-level early warning system for mastitis, while regular measurement of individual SCC allows infected cows to be identified and managed.

Somatic cell count data (both bulk milk and individual) is one of the most important health and profitability indicators, it’s not just a number, it’s a window into mastitis, milk quality and ultimately affects your bottom line.

Bulk milk somatic cell count (SCC)

Bulk milk somatic cell count is a quick, simple indicator of overall udder health at a herd level. BMSCC measures the number of somatic cells (mainly white blood cells) in your bulk tank. A high BMSCC indicates a high level of cows fighting mastitis infections (clinical and/or subclinical) in the herd. When assessing BMSCC, around 15% of cows will have (subclinical) mastitis for every 100,000 cells/ml. Sharp rises in bulk milk SCC often indicate missed clinical cases and the impact of mastitis on SCC is more pronounced when there are fewer cows in milk e.g. at the start or end of season.

Bulk milk SCC data is usually available within 24 hours of a tanker pickup, through your dairy company. Alternatively, paper printouts or tanker dockets are delivered at the next tanker pickup. Check your results for sudden daily rises, which often indicate one or more missed clinical cases. This is particularly common in herds running high cell counts. When it comes to BMSCC, patterns matter more than a single snapshot. Identify trends across the season, is there a slow trend up or down or any sudden spikes.

What to do if bulk milk SCC is rising

If you're getting close to penalty levels, act early:

In all herds, a sudden increase of 50,000 cells/mL or more may indicate that one or more clinical cases have been missed. The impact of clinical cases will be more noticeable for smaller herds, or when there are fewer animals in the herd, such as at the start or end of the season. Learn more from Technote 11.

BMSCC patterns matter more than a single result. One test doesn’t tell the story – history does. Look for:

• Consistently low = good cow
• Spike (low - high) = new infection
• Always high = chronic infection
• Up and down = unresolved issue (often a chronic infection)

If high BMSCC is not addressed, it will ultimately impact your bottom line through:

• Milk payment penalties.
• Lost production.
• Increased clinical mastitis cases.
• Ongoing treatment costs.
• Higher culling rates.

Key drivers to controlling BMSCC

1. Herd test - At least bi-monthly herd testing (around 4 tests per season). Track your herd after every herd test. Check your percentage of cows with increased SCC and watch heifers closely.
2. Monitor SCC - Find high SCC cows with RMT. These should be more closely inspected for clinical signs or excluded from the vat. Heifers can be the early warning group. Aim to keep at least 85% of heifers below 120,000 cells/mL all season. If they go above that, infection is likely spreading in your herd.
3. Talk to your vet - Every farm is different, but it may not be economical to treat high SCC cows with antibiotics during lactation unless they show clinical signs. Talk to your vet before making decisions.
4. Reduce the spread in the shed - milk chronically infected cows last or as a separate mob all together. If possible, use drafting systems to pull out high SCC cows before milking. This helps protect clean cows from picking up infection during milking.
5. Get help if you need it - A second pair of eyes (vet, milk quality advisor) can help you spot problems with your system to prevent mastitis. Use SCC data alongside your vet’s advice to guide dry cow therapy and culling decisions.

Individual cow somatic cell count (SCC)

While bulk milk SCC acts as an early indicator for mastitis, individual cow SCC identifies which cows are infected and this is where the real decisions and real gains can be made. Reviewing individual cow SCC regularly (at least 2 monthly or 4 times a season) enables you to monitor your herd and make decisions throughout the season.

Reviewing individual cow somatic cell counts (SCC) regularly, can help you:

• Monitor udder health through the whole lactation and prevent new infections.
• Identify cows pushing up your bulk tank SCC so you can milk them last.
• Make better mastitis management decisions during the season.
• Reduce the spread of infection in the herd.
• Make better decisions around dry cow treatment.
• Build a culling list based on real data and removing chronically infected cows.

Ensure milk is suitable for the vat

Protecting the vat starts with making sure only clean, saleable milk goes in. One cow with clinical mastitis, high SCC, or milk still under withholding can cause a bulk milk grade and cost you money, while putting your supply record at risk. Colostrum cows are the gate keepers of early season mastitis.

Before colostrum cows enter the milking herd, always:

• Check for clinical mastitis.
• Confirm milk withholding periods have cleared.
• Ensure they are RMT negative.

The first few weeks of supply are high risk. Undetected mastitis is a major cause of bulk milk grades early in the season. Transitioning cows from the colostrum herd to the milkers without properly checking them is a common (and avoidable) reason for a grade.

Ways to manage herd somatic cell count