Dr. Jeff Reneau, Professor and Extension Animal Scientist – Dairy Management
Dr. Russ Bey, Professor, Veterinary Biosciences

June 11, 2005

Are you a control freak or are you of the mind to live and let live? Well, when it comes to holding bulk tank somatic cell counts (BTSCC) in check this summer we hope you are a mastitis control freak!

Everybody knows that BTSCC increases during the summer. The average BTSCC increase on Minnesota herds during the summer months is approximately 75,000 to 100,000 higher than the cooler months of the year. In fact, we have come to accept it as an unalterable fact. But, does it have to be this way? Could you do a better job to keep BTSCC at a low level this summer?

Study of BTSCC records in Minnesota dairies well known for their ability to maintain low BTSCC year around demonstrate it is possible. One striking feature that distinguishes these dairies is a very low day-to-day BTSCC variation, ranging from only 10-20,000 BTSCC. This is outstanding! These dairies can be characterized by a single word…consistency. Equipment is always clean and functioning properly, personnel follow established procedures carefully, and the cows are clean (especially teat surfaces) year around. We are not surprised by this observation. Several University studies in the U.S. and Europe have verified that this is true.

There has been a lot of recent talk about the changing mastitis pathogen profile these days. Some are saying, “things are not what they used to be and maybe that is the problem.” It is true that things have changed. Today environmental mastitis pathogens (Coliforms and environmental streps) account for most clinical and subclinical mastitis on dairies. Based on University of Minnesota Udder Health Lab data, 80% of all mastitis cultures during 2000-2003 indicated an environmental pathogen origin (see chart). Several years ago, Ohio State researchers found that 82% of all clinical cases in 9 modern freestall dairies were caused by environmental bacteria. This is especially true during the summer months where they found exposure to environmental pathogens very high in bedding.

During the summer, bacteria grow at rates 300-500 times faster than during the cold winter months (40° F or less). During the summer wherever the cow lies down, bedding or pasture surfaces can be teaming with bacteria. Unless we take aggressive management steps to minimize exposure, teat surfaces will be contaminated with lots of environmental bacteria, many of which are mastitis pathogens. Both the cow’s hygiene and cleanliness of the cow’s environment are much more important during summer than during winter.

It is worth reminding ourselves that whatever is on teat surfaces needs to be removed prior to milking or the risk of creating a new mastitis infection increases dramatically. A routine (monthly) bulk tank bacteria culture is an excellent means of gauging how well you are doing. High levels of the environmental bacteria in the bulk tank milk indicate that you need to be doing a better job at pre-milking cow prep or bedding management. In fact you need to do A LOT BETTER during the summer to have the same effect as during winter.

With the warm summer months now upon us, are you ratcheting up your mastitis control or are you letting the bacteria take charge? What exactly do you need to do? We suggest the following:

Milking procedure

• Work consistently harder. Remove all dirt and manure from all teat surfaces prior to each milking. You will be amazed at what just 5 seconds more prep time could do.
• Be sure that the pre-dip coverage is excellent (covering the entire teat surface) and that the pre-dip contact time is at least 30 seconds before you wipe the teat dry. The pre-dip must be in physical contact with the bacteria long enough to kill them.
• Make an extra effort to dry the teat surfaces including the teat end.

Bedding management

• Bed stalls more frequently. Clean and re-bed the back one-half of every stall every day when using organic bedding (sawdust, straw, etc). Once every week sweep all the bedding out of the stall and start over. Even when using inorganic bedding like sand, application of fresh clean sand should be more frequent during the summer months. Periodically all the used sand will need to be removed.
• What about those dry cows? What is their environment like? You can do a bedding culture to see what teat exposure there is. Dry cows are particularly vulnerable to highly contaminated bedding materials.

Ventilation

• Housing facilities need good ventilation not only to reduce heat stress but to keep bedding surfaces dry. Bacteria require moisture to grow so if you deprive them of this critical nutrient they cannot grow.

Cow hygiene

• Clean cows have lower SCC.
• U of MN research shows that cleanliness of lower rear legs and udders correlates to individual cow SCC.
• Each one unit improvement in cow hygiene score will result in a 40-50,000 SCC reduction.

Cow health factors

• Reduce heat stress since it will depress the cow’s immune system.
• Feed cows balanced diets and minimize depressed feed intakes especially during the dry period and early lactation. A negative energy balance will decrease immune system function making cows more susceptible to getting new mastitis infections.

Keeping BTSCC lower than 200,000 is possible year around. It will take at little more consistent effort during the warm months of the year but it is well worth it. For more detailed information, visit the dairy extension web site (www.extension.umn.edu/dairy) and click on “Quality Counts.”