What is Oxidative Stress and How Does it Effect Immunity?
Oxidative stress is the broad term that relates to impairment of immune function. The production of free radicals (reactive O2 species – ROS) leads to oxidative reactions – part of the normal mechanism of defense for the dairy cow. If these oxidative reactions are out of control, this represents an imbalance of the antioxidant capacity of the dairy cow.
In dairy cattle, there are both environmental stressors such as disease-causing agents, and metabolic challenges associated with calving and milk production that can accelerate poor health throughout the production cycle. In addition, exposure to bacteria, viruses and mycotoxins during a physically demanding and stressful phase of a dairy cow’s life cycle can lead to more severe illness and production losses.
Antioxidants and Proper Nutrtition
Supplying adequate levels of anti-oxidants may help decrease damage by free-radicals (toxic compounds which damage cells in the body through oxidation) by preventing fat oxidation and preserving the ingredient in food/feed (feed anti-oxidants) or preventing oxidative damage to cells in body.
Providing adequate levels of feed anti-oxidants will help preserve other anti-oxidants for their role in preventing oxidative damage to cells.
Key Antioxidants to Boost Immunity
Tocopherols (Vitamin E metabolites)
Including adequate levels of vitamin E will improve immune status; especially when animals are under stress (transition period). Research would indicate that feeding excessive levels of vitamin E can create a pro-oxidant effect and create immune challenges for the cow.
Carotenoids (Vitamin A precursors and metabolites)
Provide adequate vitamin A (>100,000 IU/day). Chew et al. added beta-carotene and a low level of vitamin A (53,000 IU/day) and had a similar response to adding “high” levels of vitamin A (173,000 IU/day) in relation to mastitis and SCC.
Selenium (Glutathione peroxidases)
Selenium represents the glutathione peroxydases family of antioxidative enzymes that causes a reduction of oxidized molecules. Inorganic selenium (sodium selenite) is a very effective source of selenium but producers may wish to incorporate organic selenium from a selenium-yeast source if there are antagonistic elements (iron, sulphur) in the water or feed that may inhibit selenium absorption. Organic selenium should be considered during the transition period and during periods of low DMI.
Trace Minerals (copper, manganese, zinc)
Copper – High levels of copper can become a potent pro-oxidant and raise concerns about the oxidative balance. Feeding proper but not excessive levels of copper is recommended. Use proper forage analysis to check copper levels in the forages to ensure that these levels are not excessive.
Yeast Cell Wall
MOS (mannanoligosaccharide) interferes with pathogen colonization by binding receptors on the surface of intestinal pathogens, thereby blocking pathogen adhesion to the lining of the gastrointestinal tract. Dietary ß-glucans have been shown to be directly immune-stimulatory, where activation is initiated in the intestinal epithelium. This stimulation is suggested to make the animal more prepared to handle infection.
TAC Levels the "Ideal Steady State"
The relevance of vitamin E and ß-carotene in dairy nutrition and udder health is well documented in the literature (Smith et al. 1984; Weiss et al. 1990). The delicate balance and interrelationship between antioxidants and potential pro-oxidants (Cu-Zn-Fe-Mn), some of which are part of the antioxidant enzymatic systems, is well described by Miller et al. (1998).
In human nutrition studies there is plenty of epidemiological evidence suggesting the association between consumption of diets rich in fruits and vegetables and decreased risk of cardiovascular disease, hypertension and certain forms of cancer. “The beneficial effect of a high intake of fruits and vegetables may rely not on the effect of well characterized antioxidants, such as vitamin E, vitamin C and ß-carotene, but rather on some other antioxidants or non-antioxidants, phytochemicals or a concerted action of different compounds present in these foods.” (Guohua et al. 1998)
It follows from the above literature that the antioxidative status cannot be taken in isolation but rather will be the total effect of external and internal contributors to an ideal steady state.
Trouw Nutrition/Shur-Gain has applied a method to determine total antioxidant capacity (TAC) of the dairy cow in research and field trial settings. This research conducted by Shur-Gain demonstrated that TAC level in the cow may be influenced by season of the year, stage of lactation, parity, and nutrition. This original research led to the selection and amounts of antioxidants recommended for dairy cattle managed under stressful conditions.
The goal of Trouw Nutrition/Shur-Gain’s immunology program is to define and promote a positive interaction between nutrition and immunity to disease.
Contact a Dairy Nutrition Advisor today to get the optimal immune-boosting diet set up on your farm.