There will be a financial incentive to increase milk sales available to each farm. Assuming milk sales increase over the previous year, an additional incentive will be paid for high-quality milk as measured by somatic cell count (SCC) for the herd. The SCC is the number of cells, primarily leukocytes, per milliliter in milk. Leukocytes, or white blood cells, are produced by the cow’s immune system to fight an inflammation in the mammary gland or mastitis – either clinical or sub-clinical. The SCC also increases during a myriad of stress conditions. Monitoring SCC is especially critical in diagnosing cows with subclinical mastitis, because no visible signs of an inflammation are observed by the dairy producer. That was the original intent of the California Mastitis Test that estimates SCC of individual cows by stripping milk into a four-part plastic paddle, adding the test solution and then swirling the contents to visually measure the gel formation.
Culling cows or removing cows from the milking string is a short-term solution to quickly reduce SCC in the bulk tank. Cows with extremely high SCC will dramatically reduce the herd average. Monthly testing is usually often enough to isolate the cows with high SCC.
A longer-term approach is to improve the immune system of the cow. The immune system is improved when the cow builds immune proteins to ward off diseases. In addition to adequate protein in the diet to supply amino acids, the cow needs vitamins A and E plus minerals. Rations during the dry period and early lactation are most critical.
The trace minerals selenium and zinc have been linked to improved SCC in milk. Selenium functions with vitamin E in supporting the immune system and is often marginal or insufficient in diets of dairy cows. This is especially true in the upper Midwestern states, so research from that area is definitive but may overstate the deficiency for other states.
Selenium can be toxic to cows, so care must be exercised in calculating supplements. Zinc is in over 300 enzymes, and many are involved in protein metabolism. Supplying zinc methionine has reduced SCC by 30 percent, even in milk of cows that were managed well.
A third approach to controlling mastitis is a sound management program. Improved sanitation means simply keeping the udder clean and free of pathogenic bacteria that cause mastitis. That is very difficult in a wet climate.
Mud, water holes or dirty ponds are major sources of contamination. If used, bedding must be dry at all times. Straw and sand are the best beddings, and green wood sawdust is the worst. Sod that is free of mud and objects that might damage the udder is essential for all springing heifers and dry cows as well as milk cows.
Springing heifers should be separated from cows. An isolated “hospital” area is needed for sick cows. Milk-fed calves should be reared separately to avoid nursing each other. Flies can spread mastitis-causing bacteria. Avoid stressors such as stray electricity in the milking barn.
Finally, antibiotic treatment is optimally administered at the beginning of the dry period. Protective sealant dips are beneficial for teat protection after the final antibiotic treatment. Extreme care must be taken to prevent contamination before sealing teats. If antibiotic treatment is needed during lactation, a drug sensitivity test will help achieve success. It is extremely important to use only legally approved medication and follow the withdrawal time required. Drug residues in milk must be avoided.
Improved SCC should increase milk yield, improve milk quality, provide greater efficiency of production and improve profitability of the dairy herd. PD
References omitted due to space but are available upon request to editor@progressivedairy.com.
—Excerpts from University of Arkansas Dairy Digest, Vol. 18 No. 2
Wayne Kellogg
Professor
University of Arkansas
wkellogg@uark.edu
