Updated: Jul 27
By Eliza Burton, TRAC Graduate Consultant
Bulk Milk Cell Count (BMCC) is a test performed on dairy farms that refers to the concentration of cells (expressed as cells/mL) produced by the entire herd into the vat milk. This count is used at a farm level, by dairy processing companies and nationally to report on the milk quality. BMCC is also very commonly used to indicate the incidence and prevalence of mastitis within your dairy herd. Often farms have different approaches as to their ideal cell count, Dairy Australia mentions ‘the general limit used for dairy milk is a BMCC of 400,000 cell/ml. While there is an acceptable limit and performance target of less than 250,000 cell/ml in most farms and a ‘good’ range is below 150,000 cells/ml. Additionally, most often farms that receive milk quality awards usually have a BMCC below 90,000 cell/ml.’
Figure 1: Percentages of suppliers with annual average BMCCs ≤250 (green line), >250 to ≤400 (blue line) and >400 (red line) by calendar year; all suppliers are included regardless of the number of the calendar months with BMCCs in the year. Source: Dairy Australia
Mastitis is an inflammatory response within the immune system, resulting from an invading pathogen in the mammary gland. There are various types of bacteria that can cause mastitis, some are contagious bacteria such as Staphylococcus Aureus found in the udder tissues which can spread from cow to cow or environmental pathogens, like Streptococcus Uberis and Eschericha coli commonly found in manure, soil, and bedding materials etc. It is important to distinguish the difference when dealing with mastitis in the herd.
In response to a mastitis event, there are multiple lines of defence within the immune system with multiple cells playing key roles to fight the infection, these are called lymphocytes, macrophages, and neutrophils. Lymphocytes regulate the initiation of the immune response; macrophages recognise the invading pathogens and trigger an immune reaction by recruiting polymorphonuclear neutrophils. Macrophages also ingest the mastitis causing bacteria and left-over cellular debris. Polymorphonuclear neutrophils attack the invading pathogen directly and defend the mammary gland. The mastitis causing bacteria are then shed from the infected mammary gland causing clumps in the milk, these cells contribute to the volume of cells in the milk hence the increased overall cell count. Interestingly, just like nutrients are transported from the bloodstream to the udder and converted to milk, leukocytes are also transported to the udder as a mechanism to look out for invading bacteria which is why cell count levels are never zero.
In addition, if it is a clinical infection of mastitis, there is an enormous strain put on the immune system. It is also important to understand that an activated immune response can cost the animal significant amounts of glucose to run. As Owen Rees, TRAC Senior Ruminant Productivity Consultant states in his article on inflammation, ‘Research from Iowa State University in the USA has shown that to run an activated immune system in a non-lactation animal suffering a stress event for 24hrs could cost the animal 35.1 MJME or 2,140g of Glucose, so imagine how much glucose a dairy cow needs, remembering a cow needs 70 grams of glucose to produce a litre of milk. Therefore, if the cow is producing an average of 25 litres per day, she will need 1.75kg of glucose for milk production alone, if she is experiencing a stress event where the immune system is activated, from the research above she will need an extra 2.14kg of glucose to fight the infection, approximately requiring 3.89kg of glucose per day to maintain milk production and run an activated immune system. Glucose is essential for milk production, reproduction and brain function as well as powering the immune system, the cow’s ability to mount an immune response is dependant heavily on her nutritional status. If an animal isn’t receiving the correct nutrients, the more risk they are at having a weakened immune system, making them more susceptible to getting mastitis.
If you’re seeing consistently high cell counts in your herd, we’ve put together a checklist to follow:
Are the cows on the same routine daily?
Cows love routine, they perform best when all milking or other management routines are completed in the same way every day. The senses of milking and the predictability of a calm milking environment can prompt a good milk injection and will reduce the stress on the cows.
Are all milking staff trained in detecting mastitis and are they always wearing a new set of gloves every time they milk a different herd and disinfecting gloved hands or better yet changing gloves after treating a cow with mastitis?
Being able to detect mastitis early is crucial to reduce any further infection across the herd. Gloves should always be worn during milking and especially when checking cows for mastitis. A good practice is to disinfect gloved hands after stripping a cow with clinical mastitis, or better still, change to a fresh set of gloves, remaining clean and sanitary while dealing with a mastitis infection is important to reduce further contamination.
Early detection is crucial, so how do I do this?
Record the BMCC from the milk results daily, if you notice an increase in BMCC then it’s important to go and physically check the cows for swollen quarters, hard quarters, inflammation, behavioral changes, and overall general unhappiness. Another option is to watch the cows as they enter the dairy, has a cow changed placement within the milking queue, if so, she could be experiencing a mastitis infection.
Teat disinfectant and health
Are you applying teat disinfectant thoroughly to all surfaces of the teat immediately after the cups come off? Secondly, is the teat disinfectant mixed accordingly, is it sealed and stored out of direct sunlight?
Teat health is very important, healthy, clean and smooth teat skin will provide the best defense against mastitis pathogens, as well as making it so much easier to clean and maintain too.
Cups on timing procedure
Are the milkers putting the cups on at the right time, or too early or too late? Ensure the cups are put on at the correct time to allow for oxytocin release and milk let down.
Picking the best time to attach teat cups has benefits of cleaner & quicker milking out, improved teat condition and can result in a slightly higher milk yield per cow. Graeme Mein wrote an interesting article about fine tuning your milking system and techniques, stating teat cups should be applied 60 - 90 seconds after the cow’s teats and udder are first touched by the milker.
Work hard to minimize the use of areas on the farm that are likely to get quite muddy as that can contaminate the teats. It is important to note that if udders and teats are muddy, they should be washed then dried with clean towels or towelling before putting the cups on.
When was your last herd test?
Conduct a herd test as this will analyze a mastitis report and culture from individual cows to establish whether the pathogens responsible for mastitis are cow associated, or environment induced. A herd test will also help you identify which cows are consistently producing high cell counts enabling you to make informed decisions on their place within the milking herd.
Dry Cow Treatment
Early dry off of high cell count cows in later lactation is a good way to decrease the BMCC of the herd.
We do not want any mastitis in cows at dry off. If they have mastitis, they need to be brought back into the herd, or not dried off. They need to be treated until clear and then dried off. If cows have persistent mastitis that does not clear up, then dry cow can be used. It is uncommon for large amounts of mastitis to happen at dry off, that would be a fault of the person. It is best to keep cows close by on cereal hay and water for one week post dry off to monitor for any mastitis infections, then bring back in and treat. It is also good to recommend discussing the correct drug with your Vet and using strategic dry cow therapy use to reduce unnecessary antibiotic use on farm.
Consider culling cows that have 3 or more clinical cases of mastitis or consistently having two or more high cell counts.
Culling cows with high counts will help to reduce the contamination across the herd and reduce the total cell count.
Test the water quality and use the best quality water available for washing and cleaning, this will reduce the number of contaminants.
Are the cows suffering from heat stress?
When the cows are exposed to prolonged periods of heat they will often try to reduce their own metabolic heat production, they do this by decreasing their dry matter intake and milk synthesis. The heat stress event causes a cortisol response that often inhibits the immune system, therefore increasing the risk of udder infection due to their already activated immune system.
Do you have a problem with flies?
Flies can carry many diseases, in particular mastitis causing pathogens – try treating your herd for flies!
Ever thought about supplementing zinc?
Zinc is known to help with keratin formation in the teat therefore keeping pathogens out of the mammary gland, reducing the risk of mastitis and increased cell counts.
Bacto count is another type of test that can be done to measure the total number of bacteria that are alive or dead. The Bactoscan is a good indicator of the hygiene of the milk not only for the milk buyer’s target for quality and shelf life, but it will also maximise milk profit and avoid any penalties. General hygiene and vat maintenance are the major contributors to Bactoscan results. It is important to check the list below if your bacto value is high.
Is the dairy getting cleaned properly after each milking. Check the key surfaces of the shed to ensure no residues are left, i.e., rails, platform etc.
If your shed is not clean, it will increase the risk of bad pathogens, increasing the risk of contamination and therefore leading to a rise in cell count. Removing Fat and Protein deposits with Chlorinated Alkaline is also important to consider as hot water does not kill the thermoduric bacteria; we need to remove their food source i.e., Fat and Protein
Ensure the vat, vat outlets and hoses are clean and free of fatty or protein residues. Make sure there is flow through all clusters during the wash cycle.
Ensure the vat is cooling at the correct temperature; 5°C or less within the first 3.5 hours after the start of milking.
At least once weekly, check the water temperature is at least 85°C at the start of the wash cycle and around 60°C at the end of the wash cycle. Ensure the chemicals are being dispensed at the correct dose rate and there are no air leaks.
In summary, we know that Bulk Milk cell counts are a very helpful measurement to detect mastitis in our dairy herd. Recording these results daily helps us to understand & assess the health of our cows but also gives us an insight into how well our procedures and processes are working to help reduce high cell counts in the herd. We also know that mastitis/high cell count can have a large affect on the cow’s immune system and can take away glucose from other important body functions, like milk production, ultimately impacting the businesses bottom line hence why we need to pay close attention to this issue.
Remember we're here to help, so if you're seeing consistently high cell counts or recurring mastitis infections in your herd and you'd like to go over your options, please get in touch with your local TRAC Expert In Ruminant Productivity
on 08 8733 1888 or email us at email@example.com
EXPERTS IN RUMINANT PRODUCTIVITY
0427 243 319
0429 437 823
0457 243 319
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