When faced with a modest mastitis problem on the mi l k l ine , mo s t dairy specialists suggest that dairy producers look beyond the few visible or clinical cases of mastitis. They often stress to keep a watchful eye on the bulk tank and individual cow somatic cell counts (SCC). These records are often a picture of unseen bacterial invasions affecting many of your cows’ udders, better known as subclinical mastitis. Not only can a through SCC review of your herd unmask an unhealthy mastitis situation, but it is directly proportional to loss of milk production and milk quality. Dairy producers who take effective corrective actions that successfully reduce a high SCC in the dairy barn and prevent it from reoccurrence, only increase their bottom line.
High SCC and how it affects the health and performance of a dairy herd is not particularly hard to interpret. Somatic cells are a combination of sloughed body cells, which originate from the internal workings of the udder and disease-fighting white blood cells (known as leucocytes) that are generated from the immune system.
When pathogens such as staphylococcus aureus bacteria, known to cause mastitis, invade an unprotected udder, the white blood cells from the immune system dramatically increase in proportion to the body cells in order to produce an anti-disease response. It is widely accepted that SCC of less than 100,000 cells/ml of milk denotes uninfected individual dairy cows, while cows greater than 300,000 cells/ml indicates a cow with at least one infected quarter. Penn State research (1984) verifies that at least 60 per cent of cows with a SCC of over 500,000 or greater are infected with serious mastitis-causing organisms.
It’s no secret that high SCC directly and negatively affects good milk performance in most dairy herds. Consider the following relationship between SCC and milk production outlined in the following table (Philpot and Nickerson, 1991):
In addition to these milk production losses, there is also a loss of milk quality to the milk that is produced by high-SCC cows. White blood cells from high-SCC milk contain proteolytic and lipolytic enzymes that respectively breakdown valuable milk protein and fat. As a result, milk processors do not want high-SCC
milk because; for example natural casein protein levels are significantly lower, which negatively impacts such milk end-products such as cheese yield. There is also some evidence that SCC deterioration of milk leads to reduced fluid milk storage life.
It’s frustrating to allow SCC to take the upper hand in a dairy barn and thereby affect otherwise good production and milk quality. With SCC information from several possible sources such as DHI records and bulk tank slips, dairy producers should outline a plan of action and put it into place that targets high SCC cows and prevents the factors that cause them.
Here is a list of such suggestions for a workable mastitis combat plan:
Review the economic worth of moderate to high SCC dairy cows — some cows are simply high SCC producers, regardless of a well-implemented mastitis prevention program. If they are high milk producers and produce a calf every year, one should evaluate her profit contribution to the herd and decided whether to keep or cull her.
Consider culling five per cent of the herd based on extreme SCC counts and persistent mastitis infections. Three or four cows in a herd of 100 often are responsible for 30 to 40 per cent of the high bulk tank SCC. Granted, it does become a bit of a “numbers game,” but getting rid of a cow with a 1 million SCC in a 100-cow herd lowers the overall bulk tank SCC average by 10,000 counts.
Continue with sound mastitis- prevention programs — implement good cleaning and dipping teat protocols as well as practise sound milking procedures. Make sure that all milking equipment is in good working order with a good daily sanitizing program. Consult with your veterinarian for a recommended milking and dry cow prevention and treatment program.
Fight mastitis when cows are resting — good management of bedding will keep most mastitis-causing bacteria off the cows’ teat ends and out of the udder. Hydrated lime reduces bacteria growth in straw or wood shavings, but this antibacterial effect last less than two days. Therefore, a daily application is necessary. Whether organic
*based on 14 –15,000 lb. milk/cow/year
or inorganic bedding is used, a well-maintained stall should have adequate bedding. Up to six inches of straw, sawdust, wood shavings or sand should be put down and fill holes or bare spots. Stalls should be frequently groomed, where wet spots and extra manure can be simply removed.
Tackle mastitis infection problems — the rate of new mastitis infections are the highest during the first two weeks of the dry period and two weeks prior to calving. It is important to work with your veterinarian in order to identify the most effective antibiotic programs tailored for your dairy farm. Research shows that mastitis infections are eliminated by four means: 1) relying on the cow’s natural immune system, 20 per cent effective; 2) lactation treatments, 30 to 90 per cent effective; 3) dry cow therapy, 90 per cent effective and 4) culling mastitis problematic cows; 100 per cent.
Lower SCC with nutrition — feed organic zinc, selenium and high vitamin E to the dairy herd. Zinc methionine has been shown to stimulate keratin production; the tissue that forms a protective plug in the teat canal. The recommendation for zinc methionine to lower SCC is 50 mg/kg of the total ration. Selenium fed at 0.3 mg/kg diet (six mg/head/d), working with 500 iu/head/d of vitamin E during lactation and 1,000 iu/ head/d during the dry period helps reduce SCC in lactating dairy cows.
Dairy producers that get as much SCC information about their own situation and strategically work the above suggestions into their own day-to-day operation increase the chance of lowering even the most persistently high SCC amongst the cows. As a result of such conscience efforts, a dairy herd that is successful in producing milk with the lower somatic cell counts tends to lead to better milk production, quality and better farm revenue.
PeterVittiisanindependentlivestock nutritionistandconsultantbasedinWinnipeg. Toreachhimcall204-254-7497orbyemailat [email protected]
It’s frustrating to allow SCC to take the upper hand in a dairy barn and thereby affect otherwise good production and milk quality.
SOMATIC CELL COUNTS AS RELATED TO MILK LOSS
Estimated milk loss (lb./year)* % milk loss 400 3