Milk Quality in July

It’s July in Kentucky: the thermometer is rising, the corn is growing, and- milk quality is getting trickier to manage. With the warm temps and wet weather we’ve been experiencing this summer, make sure milk quality isn’t the elephant in the room.
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Two common measures of milk quality are somatic cell count and the preliminary incubation count.

Somatic cell count (SCC) is the measure of inflammatory cells responding to an infection in the mammary gland and can be analyzed from a milk sample. A SCC of greater than 200,000 indicates mastitis. If there are visible symptoms, such as abnormal milk, heat, or redness in the udder, it is a clinical case of mastitis; otherwise, the case would be considered subclinical.
 
Preliminary incubation (PI) count is a test that can detect bacteria in cold environments and is detected by holding milk at 55 degrees for 18 hours (1).
 
While milk quality issues may be more prevalent in the summer because of the ideal conditions for bacteria to grow in the environment, keeping SCC and PI count in check year-round is important for several reasons:
 
1) Mastitis has lasting impacts on the cow - Cows that experience clinical mastitis are not likely to return to premastitis milk yield and losses can be as significant as more than 1,200 lbs of milk for a single lactation (2). Severe cases of mastitis can cause permanent damage to udder tissue and loss of functionality, resulting in long-term yield loss. Mastitis also has a negative impact on reproductive health, including delayed heats, decreased preg rate, and increased risk of abortion (3).
 
2) Cost of treatment - While costs vary significantly based on treatment methods, a study in 2015 found the average cost of a case of mastitis to be $444 (4). This included treatment costs, milk loss, and death loss. With increased pressures surrounding antibiotic usage, many producers' approach to mastitis is to cull high SCC cows, which is an effective yet expensive method considering rising costs of both buying and raising replacements.
 
3) Indication of required maintenance - High PI count points towards 2 things: cleanliness issues in cows at milking or equipment that isn’t working properly to stay sanitary. Either way, failing to address the root cause of high PI count can result in more issues, including mastitis and improper milk collection, cooling, and storage.
 
4) Meeting market expectations – While the legal limit for Grade A milk in Kentucky is a SCC of 750,000, milk cooperatives have lower limits for SCC and PI to ensure that the company is able to provide high quality milk products to consumers. Besides saleable limits, other considerations include the potential for bonuses for good milk quality, penalties for poor milk quality, and competitiveness of your operation to seek out other markets. SCC should stay under at least 400,000 to maintain your market, while counts under 200,000 are considered good quality. PI counts less than 10,000 cfu/mL are typically considered low.
 
If this summer heat and humidity has you dealing with milk quality issues, reach out to your local KDDC consultant for an evaluation of milk quality on your farm through our MILK Counts program. Services are free and offer action-based solutions to your SCC and PI count issues.

1. Reeves, S., & Amaral-Phillips, D. M. (n.d.). Factors that Increase PI Count in Milk. Retrieved from UK College of Agriculture, Food and Environment.
2. P.J. Rajala-Schultz, Y.T. Gröhn, C.E. McCulloch, C.L. Guard. 1999. Effects of Clinical Mastitis on Milk Yield in Dairy Cows. Journal of Dairy Science. 82:1213-1220
3. Risco, C. A., and M. O. Dahl. "Effect of inflammatory response related to mastitis on dairy cattle reproduction." Clinical Theriogenology 10.3 (2018): 253-257.
4. Rollin, E., K. C. Dhuyvetter, and M. W. Overton. "The cost of clinical mastitis in the first 30 days of lactation: An economic modeling tool." Preventive veterinary medicine 122.3 (2015): 257-264.