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Contagious mastitis is effectively controlled by teat dipping, along with antibiotic treatment of dry cows and removal of chronically infected cows. This form of mastitis comes from Strep. and Coryne. bacteria, passed from cow to cow with few signs ever seen.
Environmental mastitis, however, presents greater challenges. Caused by more virulent Strep. and E. coli bacteria in the cows' surroundings, including the milking parlor and barn bedding, it can be a problem even in well-managed, high producing herds.
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Is an essential component of coenzymes in carbohydrate, fat and protein metabolism. The energy-producing TCA (TriCar-boxylicAcid or Krebs) cycle also depends on biotin. Biotin is important in thyroid and adrenal gland function, as well as in the reproductive tract and nervous system.
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The role of good nutrition in disease prevention is recognized. It's well documented that with adequate dietary vitamin E levels, the incidence and severity of environmental mastitis is reduced, and that selenium also plays an important role.
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For example (Smith et al., 1984), cows fed 1,000 IU per head per day of dietary vitamin E during their dry period, and injected with 1 mg of selenium per kg body weight at 21 days before calving, had 37 percent less incidence of mastitis than a control group (Figure 1). In cows that did contract the disease, those fed vitamin E/selenium showed a 42 percent decrease in the duration of mastitis compared to the control group (Figure 2). The most recent research at the University of Tennessee also showed reduced somatic cell count throughout first lactation in heifers fed adequate vitamin E and selenium.
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The key word in the research is "adequate." There's a difference between the levels of vitamin E required to avoid clinical deficiency as seen in white muscle disease and the levels shown as adequate to permit optimum health and performance. While clinical deficiency is essentially a thing of the past, most herds have not yet received the levels required to achieve their genetic potential.
Every dairy has different feedstuffs with varying levels of vitamin E. Before an adequate supplementation level can be determined, the dairy's nutritional program must be analyzed. Once that is done, in most cases it will be found that the basic vitamin E requirements are met but not the level needed to permit the desired economic effect.
On lush pasture, vitamin E intake may range up to 3,000 to 4,000 IU per head daily. In confinement, feedstuffs often provide less than 300 IU/day, with wide variations from farm to farm; even on the same farm, variations occur with different feeds.
For dry cows, 1,000 IU of supplemental vitamin E per head daily is usually adequate. Since lactating cows normally get higher-quality forage and more of it, 500 to 600 IU of supplemental vitamin E per head daily is normally enough in that period. Feed supplementation programs are the most practical, but there may be instances where injecting vitamin E is beneficial to generate a rapid rise in effective blood and tissue levels of this nutrient.
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Various research shows how vitamin E may be involved in the body's defense against mastitis. The first is based on its function as a cellular antioxidant. The entry of bacteria into the mammary gland area triggers mobilization of immuno-cells known as polymorphonuclear neutrophils, or PMNs, as well as macrophages from the blood. PMNs engulf the bacteria and then release highly reactive "free radicals" that are destructive to the body's cells. However, unless there is sufficient cellular antioxidant present, the free radicals also oxidize and severely damage the PMNs. Adequate vitamin E levels in the PMNs allow a more active and more prolonged effect of a cow's natural immune system on invading bacteria (Figure 3).
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Vitamin E also works in more generalized but less fully understood ways to affect immuno-responsiveness, says research scientist Dr. Larry Smith at The Ohio State University. It reduces circulating cortisol levels, as well as prostaglandin concentration in teat ends. Since high prostaglandin concentrations relax smooth muscle tissue, these could affect closure of the teat ends, decreasing the effectiveness of this primary barrier.
Vermont research (Politis et al., 1995) studied the relationship of vitamin E and chemotactic responsiveness, or the speed with which macrophages and PMNs attack invading bacteria. Earlier research at Ohio State (Hogan et al., 1990) found that during early lactation, when the incidence of mastitis increased, plasma vitamin E concentrations were lowest. In addition, neutrophil function decreased. In the Vermont research, the PMNs in the unsupplemented animals produced only half the superoxide anion after calving as they had before. And blood macrophages produced 15 percent less interleukin 1 (IL-1) and 35 percent fewer major histocompatibility (MHC) class-II antigens after calving.
Superoxide anion is itself a potent free radical in attacking invading bacteria, and is usually accompanied by a series of other reactions that generate even more toxic radicals. IL-1 is known to stimulate immune functions by activating T and B lymphocytes, and MHC class-II antigen enables the macrophages to function effectively as antigen-presenting cells.
With dietary vitamin E supplementation, the cows' plasma vitamin E levels increased by 10 to 50 percent over controls' during the treatment period. Meanwhile, the supplemented cows' production of superoxide anion, IL-1 and MHC class-II antigens remained at precalving levels. Supplementation consisted of 3,000 IU/head/day, fed from four weeks before expected calving until eight weeks after, and a single injection of 5,000 IU of vitamin E one week before expected calving.
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The results of a nine-herd commercial study, by Dr. Bill Weiss of The Ohio State University at Wooster, showed consistent, negative correlations between dietary vitamin E supplementation and the incidence of clinical mastitis. The higher the level of vitamin E fed, the fewer cases of mastitis were observed (Figure 4). Just as convincingly, in an on-farm split-herd study on 11 dairies, increased levels of dietary supplemental vitamin E were associated with reduced somatic cell counts in all of the herds (Figure 5).
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The evidence clearly demonstrates that adequate vitamin E is essential for any mastitis control program, says Smith. Vitamin E supplementation, with the other good management techniques that producers now understand and use, may enhance the effectiveness of the total program--and most importantly, the producer's bottom line.
References:
- Hogan, J.S., et al. 1990. Relationships Among Vitamin E, Selenium, and Bovine Blood Neutrophils. J. Dairy Sci. 73:2372.
- Politis, I., et al. 1995. Effects of Vitamin E on Immune Function of Dairy Cows. Am. J. Vet. Res. 56(2):179.
- Smith, K.L., et al. 1984. Effect of Vitamin E and Selenium Supplementation on Incidence of Clinical Mastitis and Duration of Clinical Symptoms. J. Dairy Sci. 67:1293.
- Weiss, W.P., et al. 1990. Relationship Among Selenium, Vitamin E and Mammary Gland Health in Commercial Dairy Herds. J. Dairy Sci. 73:381.
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