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.
Proper parlor management is key to ensuring high milk quality. The parlor must be properly functioning, which includes the correct teat end vacuum level, proper amount of air-flow capacity in the system and pulsators that are functioning as they should. A sign of improper milking equipment function is teat end damage, which can be seen by cracks and also hyperkeratosis (cauliflower appearance of the teat end). A proper functioning parlor also includes the proper milking procedures. The use of an efficacious pre- and post-milking teat disinfectant is an absolute must, as well as the use of gloves and single-use towels. I suggest cows be prepped in sets of 4 or 6 depending on the size of the parlor, number of employees working and efficiency of the parlor. Always starting with cow number 1 in each set, I recommend the milker strip each cow into a strip cup, and coming back to cow 1, apply the pre-dip to each cow in the set. The dip must remain on the teat-ends for 30 seconds to allow for enough time to kill the bacteria on the teat skin. A second important time-frame to remember is the time from first tactile stimulation (either wiping or stripping, depending on your order, in this case stripping) to unit attachment should be approximately 90 seconds to allow for full milk letdown. Ensuring these time frames have been met, the milker can wipe cow 1 with a single use towel and attach the unit, then move to the rest of the cows in this set. Procedures must be monitored very closely to ensure every milker in the parlor is prepping all cows properly. Units should be attached to clean, dry and properly stimulated teats at every milking.
Finally, I suggest a California Mastitis Test (CMT) be performed on all fresh cows prior to their milk going in the tank. The best chance to cure an infection is during the early postpartum period, prior to the infection becoming chronic. Therefore, any positive quarters should be cultured immediately and treated when possible. Cows with a contagious infection should be removed from the herd or milked last. Also, it is absolutely essential to focus on maintaining a clean and dry area for calving as well as for fresh cows. Calving stresses the immune system, increasing risk for new mastitis infections. Ensuring a clean and dry environment will help reduce this risk.
These recommendations will help producers proactively lower their bulk tank SCC. Producing milk of the highest quality not only benefits the processor and consumerthrough increased shelf life and improved taste, but also benefits you through long-term profitability.
Source: Christina Petersson-Wolfe Extension Dairy Scientist, Milk Quality & Milking Management