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Maintain Oxidative Balance to Minimize Mastitis
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James Spain, Ph.D.
Professor of Animal Science
University of Missouri |
Dairy producers make management decisions to allow cows to achieve optimal levels of milk production. Optimizing milk production is achieved through a total management system that positively affects the cow’s health. Systems that sustain the herd’s health lead to the most efficient levels of milk production as well as reproduction. A key aspect of dairy cow health is obviously the health of the mammary glands. Dairy farm managers have long known cows suffering from mastitis have a negative effect on farm profits. This article aims to discuss how a strong defense to mastitis is a strong nutrition program. It will touch on the causes of mastitis, how oxidative balance plays into that and the role of nutrition as essential to keeping cows healthy.
Anyone who has spent even a limited amount of time on a dairy farm quickly learns how to detect and treat a case of clinical mastitis. The outward appearances of a mastitis infection are inflammation, reddening of the udder, abnormal milk (clots, flakes, strings), elevated temperature to the touch of the infected quarter, loss of productivity and discomfort for the animal. A clinical case of mastitis is easily observed. Because of easy detection, farm managers and employees can take quick action to treat and support cows diagnosed with clinical mastitis. The loss of income and the expenses associated with clinical mastitis are also easy to measure – lost milk production, milk discarded after antibiotic treatment, veterinary care costs (antibiotics), and farm labor. And while clinical mastitis does result in lost income, subclinical mastitis can create a significant loss of farm income that is much less obvious.
Subclinical mastitis is the infection of the mammary gland that does not result in the outward signs exhibited when fighting a clinical mastitis infection. Because it is a “hidden” or “silent” mammary gland infection, farm managers must take steps to diagnose subclinical mastitis using other technologies. One of the most relied upon measurements of mastitis detection on dairies today is monitoring somatic cell count (SCC) of both individuals and the bulk tank. While these measurements allow for monitoring at the 40,000-foot level, the underlying challenge is not manifested in outward signs. These challenged cows are likely taking as much from the milk check as their clinically manifested herd mates. So, while this article is not intended to make us all experts in the immune system, it is important to understand a few of the key components of the cow’s defense system. It is also important to understand the key role of nutrition on immune function and how the nutrients we put into our cows may influence their ability to fight mammary gland infections most effectively.
It is understood that most cases of mastitis are due to microbial invasion of the teat canal. This results in a breach of the first line of defense. Once the teat is invaded, the cow next relies on the internal, or innate, immune system. Macrophages and neutrophils can be broadly described as white blood cells and make up a large portion of the somatic cells measured in the milk of cows suffering from mastitis! These white blood cells are known to play an active role in fighting microbial infections. Neutrophils are known to be involved in the inflammatory response during an infection. During the battle between neutrophils and invading microbial organisms there is a release of reactive oxygen species (ROS). The most discussed ROS are the superoxide anion (O-2) and hydrogen peroxide (H2O2). The release of ROS is an effective method to remove microbial invaders; it is akin to ‘biological bleach.’
However, the ROS do have side effects. This biological bleach (a natural chemotherapy of sorts) also has the ability to damage host cells. This damage results in collateral injury to the cow’s mammary gland. The cellular and tissue damage caused by this battle between the cow’s immune system and the invading disease causing bacteria must be cleaned up by the cow’s immune system. The cow’s method to clean up the ROS is the antioxidant system. If left unchecked, the ROS will continue to damage the mammary system resulting in damage to proteins, fats and DNA. The steps to effectively neutralize these ROS to water are the enzymes glutathione peroxidase and superoxide dismutase. So these two enzymes help minimize the overall damage and long term injury that a mastitis infection inflicts on the mammary glands. In other words, without these enzymes working at maximum effectiveness, the ROS are able to overcome the cow’s antioxidant checks and balance system. The overabundant supply of ROS then results in oxidative stress. So it is critical that these enzymes function properly. In order to optimize the antioxidant checks and balance system, these enzymes must be supported with required trace minerals such as selenium, zinc, copper and manganese.
These antioxidant nutrients are well documented and are often discussed when formulating for mammary health. Indeed, two minerals and one fat soluble vitamin have been identified as most critical for optimal immune function as antioxidants. Selenium and zinc have been studied and shown to be important in mastitis. Zinc serves an important role in skin health, the first line of defense. Research has shown that selenium can improve the killing ability of neutrophils, thus strengthening the animal’s defenses. The antioxidant that is involved with selenium is vitamin E. This antioxidant has also been observed to increase bacterial killing of neutrophils when supplemented. Dietary antioxidants also play a part in sparing vitamin E and reducing the load of oxygen radicals that the host has to remove. In other words, proper nutrition, including the appropriate supplementation of trace minerals and dietary antioxidants, is critical for keeping animals healthy. Proper nutrition will help prevent new infections. Proper nutrition should work to reduce the severity and duration of the infection which will decrease the tissue damage when cows do develop mastitis.
We cannot avoid mastitis on the dairy. Systems should be in place to allow the rate and severity of mastitis to be minimized. The housing and milking systems should minimize exposure to mastitis causing bacteria. These systems keep the cows clean, dry and comfortable. However, we know that no system is failure proof and when challenged, we want the cows to be prepared to respond quickly and effectively to any invading organism. Having the cows best prepared includes maintaining an effective immune system through proper nutrition, including the important antioxidants. Remember, the nutrients used for fighting infection could have been used for milk production and reproduction. So by creating an animal health management system that includes proper nutrition, we will achieve a herd with fewer cases of mastitis and more dollars on the bottom line. |
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