Missouri Dairy Business Update  
Volume 10, Number 6
June 2010

Time for Change - SCC

Authors: Barry Steevens and Scott Poock, University of Missouri Extension

The legal Somatic Cell limit for marketing unpasteurized Grade A milk is currently 750,000 cells per milliliter. The measurement of somatic cells (white blood cells) is an indirect indicator of the degree of intramammary infection in the mammary gland.  Most dairies in the United States (US) produce milk at a level lower than this upper legal limit as at that level dairy cows are experiencing some degree of subclinical mastitis. Research has clearly shown cows producing milk at a somatic cell count (SCC) level under 200,000 produce more milk, produce milk of a higher quality having a greater cheese yield and also longer shelf life. Current research data suggests when cell counts exceed 200,000 cells/ ml the odds favor the quarter is infected or is recovering from an infection. Cell counts in excess of 300,000 cells / ml and above are a clear indication the quarter has an infection and that an inflammatory response has been elicited.

Back in 1998 members of the European Union began the process to adopt 400,000 SCC as the upper limit to produce Grade A milk.  New Zealand and Australia have the same upper SCC limit and Canada has 500,000 SCC/ ml as their limit. The reason for these countries to adopt the lower limits is a higher quality product and a higher cheese yield.

Back in 2000, an effort was supported by the National Mastitis Council to change the US level to 400,000 through the National Conference on Interstate Milk shipment (NCIMS). This conference has input to changes in the Pasteurized Milk Ordinance (PMO) which is the nationally accepted document for Grade A milk quality standards. NCIMS rejected the proposed change to lower the SCC level because it was felt the PMO is a public health document and not a milk quality document. It was stated the potential for pathogens in raw milk is irrelevant because the milk is pasteurized therefore destroying pathogens that may cause a public health hazard.

Data in 2000 suggest most producers are below 400,000, but not all producers. Recently EU countries importing dairy products have requested all milk produced in the US to be less than 400,000 SCC (similar to EU). Suddenly Grade A milk quality standard became an exporting issue. Milk procurement companies cannot afford send out two trucks to pick up milk; one for milk less than 400,000 and one for milk between 400,000 and 750,000. In 2008 we were exporting 11% of the total US supply and today it is down to 7%. Currently milk prices are low and dairy farmers are struggling to financially survive. Increasing the export of dairy products will help reduce the surplus of milk in the US and increase domestic milk prices.

Most recently the nation’s largest coop, Dairy Farmers of America (DFA) voted to change their resolution from opposing reducing the 750,000 limit to encouraging all of their producers to produce the highest quality milk with the lowest possible somatic cell count.

Dairy producers have many sources of information and research to help them make good decisions in producing quality milk. National Mastitis Council has endorsed teat dipping and dry cow treatment as two of the most effective methods to control mastitis. Also we have learned how to provide a clean comfortable stall for the dairy cow. Sand, being inorganic, has been very effective in keeping the cow’s udder healthy. Mastitis causing organisms do not grow as readily in sand as other types of organic bedding such as sawdust or straw.

Recently, a 240 cow dairy (University of Missouri’s Foremost Dairy) has been able to reduce the herd SCC level to less than 200,000 since January.  This is 75-150,000 lower than historical average.  This is even more remarkable because the dairy is milking 40-60 more cows than usual.

We spoke with John Denbigh (manager) and Eric Adkins (herdsman) about the enhanced milk quality at the farm.    They quickly agreed on the fact that the student workers have been following the stall cleaning protocol with much more diligence.  Specifically, once the dirty bedding is removed, fresh bedding is placed on the stall.  Subsequently, the cows lie in clean stalls and are cleaner themselves. 

Another change has been the use of a teat dipper rather than spraying the teats at the end of milking.  We know that using a teat dipper will give you better coverage of the teat than spraying.  There has been data that shows that you will use less teat dip with a dipper.  So, you get better coverage and save money.  Along with the use of teat dipper, the teat dip was switched to a barrier dip.

Dr. John Middleton has done many milk cultures from the farm and historically, the clinical cases of mastitis on the farm were of an environmental origin.  Therefore, the barrier dip will help decrease the incidence of mastitis by these organisms.  In fact, the farm has had less clinical cases of mastitis than in the past (4-6 fewer clinical cases per month this year).

Both John and Eric felt that a few cows have been culled due to high SCC.  Along these same lines, the herd’s reproduction has become improved.  This has led to fewer days in milk (DIM) in the herd.  It is well established that as a cow’s lactation lengthened, there is an increase in SCC.  Therefore, lowering the herd’s DIM should result in a lower SCC.

Another improvement that John felt has helped is increase emphasis on hoof health.  A hoof trimmer comes on a regular basis for maintenance trimming.  Dr. Tessa Markovich brings veterinary students weekly out to treat lame cows more aggressively.  John has seen this program lead to more cows using the stalls correctly.  Once again, this means cleaner cows and less mastitis.

In conclusion, knowing what type of organism is causing high bulk tank SCC will help you target management changes.  And it is management, not treatment that will give you the most benefit.

Figure 1. MU Foremost Dairy Somatic Cell Counts

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