For decades, the legal limit for the bulk tank somatic cell count (BTSCC) in the U.S. has been 750,000 cells/mL. Above which, producers cannot ship their milk for sale. However, there has been a movement to lower the legal limit. Most recently, the National Milk Producers Federation proposed to drop the legal limit from 750,000 cells/mL to 400,000 cells/mL. This proposal was rejected by the National Conference on Interstate Milk Shippers (NCIMS). Despite this rejection, the legislation has been introduced to Congress and if enough scrutiny is raised, the lowering of the legal limit may happen in a process outside of NCIMS. The impetus to lower the legal limit has been prompted by the European Union (EU), which has maintained a a 400,000 cell/mL limit for years. EU documentation states that any imported milk product must be produced under these same guidelines. Despite our international trade in previous years, the EU is now adhering tightly to their guidelines and requiring all imported products to meet their standards. Our current limit of 750,000 cells/mL will quickly limit trade, affecting our ability to remain competitive internationally.
With this background, it is my opinion that the national limit for SCC will be lowered in the near future—making this the perfect time to review some BTSCC lowering guidelines. First, culture all cows over 400,000 cells/mL or the top 20% of the herd, whichever results in the least number of cows. This list is easiest to determine if you are enrolled in the DHIA monthly monitoring program. If you are not, this is the time to get enrolled. Once you have these culture results, refer to the Reference Guide for Mastitis-Causing Bacteria 1 to learn the source of the infections specific to your herd. Remove contagious animals from the herd or milk them last, treat those which might be susceptible to antibiotics with the help of your herd veterinarian, monitor those high SCC cows in subsequent months and repeat this process monthly.
Next, culture all cows with clinical mastitis. Again, remove contagious cows from the herd or milk them last, treat those susceptible to antibiotics with the help of your veterinarian, and monitor these cows with subsequent tests. The use of a strip cup in the parlor will help to identify cows with the early signs of mastitis. Milk from these cows and any other suspect cows should not go in the tank. You must also be willing to cull cows who do not cure. They may be a risk to uninfected herd-mates and also put an economic strain on the farm.