By Ernie Oelker
Dairy herd managers are well aware that extended periods of rainy weather in spring and summer are a major contributing factor in the increase in the number of new cases of clinical mastitis, especially in herds bedded with organic materials such as sawdust, straw or a combination of these.
Bacteria need moisture, heat and a food source to grow rapidly. A dairy manager’s preoccupation with planting and harvesting activities at this time of year often adds to the problem.
According to the Dairy Practices Council, somatic cells in milk consist primarily of leucocytes or white blood cells, but somatic cell count (SCC) also includes some epithelial or milk-secreting cells from the udder.
As of July 1, 1993, the regulatory action level for somatic cells in milk from cows and goats became those counts in excess of 750,000 per ml. Such milk is of poorer quality and abnormal composition, almost always because of mastitis infections.
Some types of mastitis cause an elevation in SCC, but do not cause any signs on the strainer or in a strip cup. This is called sub-clinical mastitis.
Every doubling of the SCC starting at around 50,000 SCC/ml costs the producer 200 to 400 pounds of milk per cow per year.
If the herd is at the regulatory limit of 750,000 SCC, total milk losses may exceed 1,500 pounds per cow per lactation. Also, as the SCC increases above 200,000, protein degradation begins and cheese yield losses increase. At 600,000 SCC loss of 2 percent of expected cheese yield is possible.
Milk that is visibly abnormal, tastes or smells bad indicates mastitis infection and is easily detectable. Most samples of such milk have elevated SCC and contain mastitis organisms that can be cultured.
However, most cows that have mastitis will show no sign of infection. It is not unusual to find herds at 750,000 SCC that show few clots on the strainer and very few clinical mastitis cases.
Withholding from sale visibly abnormal milk alone will not eliminate a mastitis problem.
A normal cow will be below 100,000 SCC. A herd average of 300,000 SCC or higher is cause for concern and mastitis control should be evaluated.
What to shoot for.
Generally accepted guidelines and goals for Somatic Cell Counts:
Herd average SCC <200,000
80% of cows <200,000 SCC
90% of cows <400,000 SCC
less than 5%
of cows >750,000 SCC
Clinical mastitis should affect less than 1 percent of cows per month. The lower the SCC that can be achieved the better.
The goal of a good mastitis control program should be to identify and eliminate the cause of the mastitis, not just treat the clinical cases and dry off animals properly. If your herd has a SCC over 200,000 or clinical mastitis in more than 1 percent of the herd each month, call your veterinarian, county extension agent and dairy field man for assistance.
Cleanliness of animals, housing conditions, udder prepping and proper milking procedures all must be evaluated. Be sure the milking procedure is properly done by every milker every time and that teats are dipped properly with a dip that is known to be effective.
Milking systems must be maintained and evaluated on a regular schedule by qualified service representatives. Teat cup liners must be changed according to manufacturers recommendations. Make sure the equipment used to milk fresh cows and treated cows is cleaned and maintained as well as the rest of the milking equipment.
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This procedure can be posted in the milkhouse or milking parlor for review by personnel as needed:
A. If teats are visibly soiled, wash them with an individual towel wetted with a sanitizing solution compatible with your teat disinfectant. Otherwise proceed to step B.
B. Completely coat each teat to the base of the udder with a teat disinfectant. Use a product that is labeled as a predip and has been shown to be effective in preventing intra mammary infections (IMI).
Be sure to cover the entire teat and allow for at least 30 seconds contact time.
C. Observe the foremilk from each teat for abnormalities. Do not strip into your hand. If you check the milk before predipping, be sure to attach the unit within 1 minute to maximize milk let down.
D. Dry teats thoroughly with individual paper towels to remove all the teat disinfectant to eliminate residues. Do not touch the teats with your hands after removing the teat disinfectant.
E. Attach the milker unit between less than 1 minute after the start of udder stimulation.
F. Adjust milker unit as necessary for proper alignment to prevent “squawks,” liner slips and air admission, especially at the end of milking when the slightest “squawk” will greatly increase the risk of new IMI.
G. Shut off the vacuum before removing the unit.
H. Immediately after unit removal, coat each teat with an effective teat disinfectant that has been shown to be effective at preventing new IMI.
When using a predip or spray, coat the entire teat.
* If recirculating dip cups are used, discard the used teat disinfectant and wash the dip container after each milking.
* In freezing weather, be sure liquid post teat disinfectant has dried or has been removed before allowing animals to go outdoors into cold temperatures.
(The author is an agricultural extension agent in Columbiana County. Questions or comments can be sent in care of Farm and Dairy, P.O. Box 38, Salem, OH 44460.)