Will Your Herd Cell Count Rise with the Thermometer?

Posted: January 22, 2008

Dr. Arlen Mills, Extension Veterinarian, Capital Region, Pa.
May 3, 2002

As the weather begins to warm up, producers often notice that the somatic cell count and the number of mastitis cases begin to rise. If we stop and consider what factors may contribute to these increases, this should not be a surprise. Somatic cells in the milk are cells that are there because of some stress or inflammation in the udder. Many of the stresses we see associated with the hot summer weather can cause an increase in SCC numbers. This may be heat stress by itself or rumen acidosis which is more prevalent in the summer. Acidosis becomes more of a problem in the summer due to the changes in eating habits of the cow in hot weather and due to the changes we make to the summer ration in an attempt to keep DMI (dry matter intake) up. Make plans now rather than waiting until the heat is upon us. Install fans to keep cows cool, and make sure space is adequate so that cows are not crowded together. Holding areas are often a farm “hot spot” so make sure these areas have first priority when it comes to cooling cows.

The other major factor contributing to this summer increase in SCC and mastitis is an increase in bacteria numbers. If we remember what bacteria need to live and thrive, it’s easy to see why we may expect them to cause more problems in the summer. Bacteria need food, water, and heat to multiply and flourish. If we can remove any one of these three necessities of life for the bacteria, we can keep them in check. If all three factors are present in ample supply, bacteria numbers will
escalate to high numbers. This large bacteria population provides many more chances to attack and perhaps infect the udder tissue. The resulting SCC is a body count of those cells that have been sacrificed in the attempt to ward of or destroy the attacking bacteria.

So to lower the bacterial numbers, let’s remove one of the necessities of life for the bacteria. We can’t do much about the temperature. If we could cool it off to slow down the growth of bacteria, we’d all be happier but that’s out of our control. Perhaps instead we can limit the food available for the bacteria. Bacteria use any organic material as potential food. This may include some bedding materials, manure, or milk. The main advantage of using sand in free stalls is that the clean sand has no organic matter that the bacteria may use as food. Sand bedding can become a place where bacteria can live and multiply if the sand becomes contaminated with organic matter, usually manure.

The other option is to remove moisture from the environment of the bacteria. Without water, the bacteria will die. Keeping stalls dry is the number one defense against bacteria. Make sure that stalls have been properly constructed to limit stall contamination with urine or manure. Time spent on a daily basis to groom and check stall areas is time well spent. Pay special attention to the back half of the stall where the udder makes contact with the stall surface. Clean, dry stalls and cows should be a priority on every dairy.

This also may be a time to review your milking procedures to make sure these are at their best to protect those teat ends from all those hungry bacteria. Are you cleaning and dipping the whole teat before attachment of the milker? Are you using an effective teat dip on all teats as the milker is removed? Wearing milking gloves may decrease the number of bacteria carried from cow to cow while milking. This is a great time to do a milking procedure “check-up.”

Something else that increases in the summer is fly number. Flies may spread mastitis organisms from cow to cow or, from the environment. Flies have been identified as a common cause of heifer mastitis. Fly control will pay dividends both in cow comfort and less risk for mastitis.

Plan ahead. Take steps now to prevent your herd SCC and mastitis numbers from rising with the thermometer.