Keeping somatic cell counts low in your herd can prove to be a real challenge during the hot summer months, when counts can soar along with the mercury. What causes these spikes? How can we prevent them? There are many answers for both of these questions, let's review some of them now.
What causes SCC to rise in the summer?
In the Midwest high temperatures are usually accompanied by high humidity. This increase in air moisture leads to less evaporation so alleyways and other barn surfaces will stay wetter for longer. Alleys in freestall barns will likely never be completely dry, and even the cleanest barn will have at least some manure present. This combination means dirty feet, and when a cow lies down, those wet, dirty hooves will come in contact with teat ends. That contact can lead to contamination. An additional source of moisture in alleyways—and especially in the feed lane—is the use of sprinkler systems to cool cows.
Stalls are another area where surplus wetness can be found. Regardless of the bedding material used and whether you keep cows in tie stalls or free stalls, the increased humidity will lead to wetter bedding. Moist, warm bedding creates the perfect breeding ground for mastitis-causing environmental bacteria. Wet alleyways and stalls both lead to the same result: a greater opportunity to introduce bacteria to the teat of the dairy cow causing a potential for higher SCC.
There are possibly other explanations as well. There is some thought that heat stress on the cow itself may actually lower her immune response and ability to fight off low level infections in the udder. Florida research suggested the summer SCC increase may actually be related to decreased milk production when cows are experiencing heat stress (Shearer and Beede, 1990). Other research, however, suggested the real culprit in the summer is the increased rate at which pathogens multiply, thereby increasing the potential for infection, mainly from environmental pathogens (Hogan et al 1989).
How can I prevent an SCC increase in the summer?
As I mentioned above, there are several answers to this question—and no one method is enough. Rather, a series of actions can be taken to help keep SCC low. First and foremost, no slacking! Cutting corners now can lead to bad habits in the future. Take the time to thoroughly clean alleys and stalls, and do so often. Keeping piled up manure at a minimum will help keep manure off of hooves, and away from teats.
In the stalls, make sure bedding is getting the TLC it deserves. There will inevitably be some manure in the stall platform, take the time to scrape it out. Also, take the time to add clean, dry bedding to the back of the stall to ensure a clean resting place for the udder. In addition to top-dressing, make sure stalls are completely cleaned out and given fresh, dry bedding regularly.
Air movement in barns helps keep cows cool, but it can also aid in drying out bedding and alleyways. Take advantage of free air movement from open-sided barns and properly placed fans. This can reduce the moisture level in the stalls and alleyways. That will help keep cleaner feet and cleaner cows. Another option to help dry out stalls and especially alleys is to let cows out on dirt exercise lots or pastures, if available. This may possibly allow some alleys to dry completely. In addition, it will give the cows some time on dry surfaces and reduce the manure deposited in the alleys. An added benefit to this practice may be healthier feet and legs because the cows are off the concrete for a few hours.
In the parlor, make sure the milking routine and equipment are kept at their highest quality level. If cows are carrying even subclinical levels of infection, it can contaminate the milking line. Poor milking practices can lead to the contamination of other cows, so extra steps need to be taken to prevent it. This includes thorough teat dipping of all quarters, and using a different towel for each cow.
Lastly, move cows slowly. Whether it is around the parlor or around the barn, moving cows slowly can prevent manure from getting kicked up onto the feet and legs. Cows moved calmly are also more likely to remain calm in the parlor. This will help them more readily let down their milk, which can prevent teat damage and other problems.
Keeping somatic cell counts low and preventing mastitis is important all year round on a dairy, but can prove the most difficult as temperatures and humidity rise. By remembering the causes of teat contamination, and actively taking steps to prevent it, dairy farmers can avoid the dreaded SCC spike in the summer months.