by: Steve Blezinger
Ph.D., PAS

Part 2

In the last issue we began a discussion of the relationships between health and nutrition, specifically minerals. Adequate or inadequate levels of any of the nutrients can have serious effects on the overall health of the cow or calf. Conversely, health conditions such as disease can likewise affect nutrition, especially the animal's ability to absorb and/or metabolize many of the nutrients. In recent years, research and practice has emphasized the effect of numerous nutritional compounds to enhance health in cattle on a number of levels. Over the years the term “nutriceutical,” has been coined to describe any number of assorted nutrients, compounds and products which can stimulate immune response in the animal or seem to have a sort of therapeutic or direct health effect. While this terminology is not popular with the FDA and other regulatory entities, it has caught on to some degree in the industry.

Some Background

For a variety of reasons, keeping animals healthy and productive often proves challenging. Especially as management programs have become more intensive with cattle moving from being raised purely in range situations. This is also the case as producers learned that they could effectively transport cattle from one location to another, in many cases long distances. Environmental conditions and the presence of a multitude of pathogens and parasites have always been factors to contend with.

Over the years producers and livestock professionals have developed an extensive array of vaccines and antibiotics (fed and injected) to aid in combating disease and infection. They have also discovered that in order for these tools to be truly effective, the animal's immune system has to be functional. The one big issue that is a matter of frustration is that we cannot “inject” immune response into an animal. The immune system's function is based to a large degree on how it developed from birth, the nutritional plane the animal is on and the availability of the components needed.

As the cattle industry began utilizing more intensive feeding protocols (i.e. feedyards or confinement feeding on high grains) and moving cattle from a forage-based diet to a grain-based diet which requires a significant shift in types of microbes found in the rumen. Researchers have found that this process can be improved and aided through the use of a number of “non-medicinal” products or compounds.

Another factor which has come into play is the consumer's perception of the healthfulness of beef products which have been produced using significant levels of any number of drugs and what many believe to be “unnatural” compounds introduced into the animal. Subsequently, general consumer belief is that, because of the use of these compounds, beef may not be as safe as it could be. For these reasons, the interest in use of nutrients, products or compounds that can be considered more “natural” is of greater interest.

But this interest does not only come from the consumer's end. Research has shown that the economic implications to producers is great when high levels of medications and antibiotics must be used to treat sick cattle. Thus the need to improve the animal's physiological defenses from nutritional sources has steadily increased and will continue to do so. Research has shown that improving the overall nutritional plane of an animal will improve its performance and overall healthfulness.

Opportunities for Application

At this point some of the greatest interest is in the area of minerals, especially trace minerals, and vitamins. The second is products that can be used in the digestive process such as yeasts, bacteria, fungi and their metabolites. These are commonly referred to as direct-fed microbials or probiotics. Other categories which could also be included include different enzymes, organic oils and nucleotides.

Nutrient Applications

As mentioned, a great deal of nutriceutical application is in the form of providing adequate or more appropriate levels of specific nutrients to the animal in order to boost immune response. Examples of these include Zinc, Copper, Selenium and Vitamin E. Research has shown that these nutrients, when properly supplemented, can enhance a cow's immunity against diseases, such as mastitis, by increasing resistance to infections and by decreasing severity of infections when they do occur. This can be related to the stimulation of the immune system. Supplemental Zn, Cu, Se, and other trace elements can alter immune function of newly received calves, and trails have shown decreases in Bovine Respiratory Disease (BRD) morbidity rate with supplementation.

Zinc is essential to all animals and plays significant roles in the metabolic activity of the grazing ruminant. Zinc functions in enzyme systems and is largely involved in nucleic acid metabolism, protein synthesis and carbohydrate metabolism. One series of studies reported a need for Zn for mobilization of Vitamin A from the liver. Zinc is found in all body tissues which are high in protein or calcified material. Its absorption appears to be directly dependent on the body's physiological need. Early effects of Zn deficiency include reduced feed intake, reduced growth rate and feed efficiency followed by skin disorders. If left untreated, other more serious conditions may appear including inflammation of nose and mouth, unthrifty appearance, stiffness of joints with soft edematous swelling of the feet in front of the fetlocks as well as a host of other deficiency related symptoms. Many of these symptoms appear to be related to the role of zinc in protein synthesis and energy metabolism. This relationship is also noted in the body's ability to produce the necessary “killer cells” which the animal's immune system uses to fight off infection. Zinc deficiencies in the animal have resulted in a decreased ability by the animal to produce these various immune system components. Providing appropriate levels of Zn, especially in a highly available form has been shown to counter act these effects and improve overall immune system function

Similarly, a large number of disorders are attributed to deficiency of Cu in cattle. Symptoms including anemia, severe diarrhea, depressed growth, hair color change and weak, fragile bones are only a few of the characteristic signs of a clinical depressed Cu status. One of the more sensitive indicators of depressed Cu is achromatrichia or loss of hair pigment. Black cattle tend to develop a red tinge to the hair coat whereas the hair of red cattle lightens considerably. Hair loss around the eye is also occasionally noted with Cu deficiency. Likewise, deficiencies in copper have been shown to reduce the effectiveness of the immune system.

One of the primary metabolic requirements for Selenium is for the production of glutathione peroxidase, a Se-containing enzyme necessary for the prevention of oxidative damage of cellular and subcellular membranes, i.e. an antioxidant, as we commonly hear the term used in human medicine and nutrition. The enzyme apparently attacks and destroys peroxides before they can damage the membranes. The production of peroxides in the body is a normal metabolic process and a constant source of glutathione peroxidase is required to counteract this activity. A Se deficiency reduces the amount of active enzyme, allowing greater amounts of peroxides to go unchecked. Selenium requirements are often categorized with those of Vitamin E which has a similar antioxidative activity in cellular membranes as that of glutathione peroxidase. Once again, an important role of Se includes adequate immune response in livestock. It also may affect prostaglandin synthesis and essential fatty acid metabolism.

Selenium and vitamin E appear to be closely tied together. One study by The Ohio State University researchers has shown that supplementation with vitamin E decreases the incidence of mastitis (infection of the mammary gland), and selenium decreases the duration of these infections. Combining selenium and vitamin E supplements appear to result in the greatest increase in defense against mastitis. Deficiencies of vitamin E and selenium also have been found to increase the incidence of retained placenta. Selenium deficiency alone can increase the incidence of embryonic death and uterine infections and can decrease fertility.

Yeasts, Microbials and Probiotics

The use of feed additives containing live microorganisms and/or their metabolites (compounds they produce as waste) to improve the efficiency of production in cattle has increased, to a large degree, as a response to consumer demand for more “natural” growth-promoting or efficiency enhancing substances. Yeast products, direct fed microbials, probiotics and other terms are used to identify a host of products that are based on populations of microbial organisms, all thought to have a beneficial role in the rumen or lower digestive tract. Subsequently the use of these materials has shown or is believed to have shown benefit by improving the digestion of various nutrients, especially forages, in the bovine digestive system.

Direct-Fed Microbials (DFM) have been of great interest in recent years. There have been several hypotheses put forth to explain the usefulness of DFM. One of the most common explanations for improved animal health or production suggests that the addition of beneficial bacteria prevent the colonization of pathogens in the lower gut by competing for space and nutrients. Production of antimicrobial end products such as acids and antibiotics has also been discussed. Some of the proposed mechanism for how DFMs work include:

•      Production of antibacterial compounds (acids, antibiotics).

•      Competition with undesirable organisms for space and/or nutrients in the digestive tract (competitive exclusion).

•      Production of nutrients (e.g. amino acids, vitamins) or other growth factors which stimulate growth and reproduction of other microorganisms in the digestive tract.

•      Production and/or stimulation of enzymes.

•      Breakdown and/or detoxification of undesirable compounds

•      Stimulation of the immune system in the host animal.

Similarly, yeast usage has found applications in many areas. One particular area of interest is in cattle grazing fescue pastures. Much of the eastern and southern United States has endophyte-infected fescue as the main source of forage protein and energy. While new lines of endophyte-free fescue exist, it is unlikely that there will be wide-spread replanting of fescue areas.

Yeast cultures have been shown to positively affect animal performance and mineral consumption. Studies in Florida and California resulted in improved feed intake, production, and reduced rectal temperatures during summer heat stress in dairy. Other research trials have shown that yeast cultures have also increased rumen bacteria numbers and improved the digestion of feedstuffs in both beef and dairy animals. Both mineral consumption and absorption have been positively affected by the addition of yeast culture to free-choice mineral mixes. Finally one 1986 study showed improved weight gains in yeast culture fed cattle grazing fescue pasture.

Much research is still needed into how these compounds actually function in the animal and what the overall mode of action really is. The results to this point, however, have been good enough that producers and researchers alike should give attention to these tools.


From this brief review it becomes obvious that animal health and productivity are not necessarily related to the application or use of a needle. It is important for the producer to evaluate the opportunities and tools at his disposal. Many of the concepts discussed here could prove valuable at improving overall animal health, performance and producer profitability. This will become increasingly important as consumer demand results in lower amounts of antibiotics and other compounds used for the production of food.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, TX. He can be reached at 667 CR 4711 Sulphur Springs, TX 75482, by phone at (903) 352-3475 or by e-mail at

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