In the previous issue we began a discussion of the relationships between health and nutrition. For years we have known that health and nutrition are �joined at the hip.� The presence of adequate or inadequate levels of any of the nutrients can have serious effects on the overall health of the cow or calf. Similarly 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 nutritionally based compounds to enhance health in cattle on a number of levels. A relatively new 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.

A number of issues have come into play in recent years which have stimulated research in this area and overall interest in nutritionally-based compounds for use in health related applications. A field once the responsibility of veterinarians may be opening up to require the input of nutritionists, microbiologists and others as the animal health industry learns more about the affects that nutrition plays in health maintenance and the stimulation of immunity.

Let's take a look at some of the implications of this trend and where potential advantages could lie for the cattleman.

Some Background

Since man began managing livestock two of the most significant issues he has faced have been nutrition and health. Keeping animals healthy and productive has, in many cases proven quite challenging, especially as management programs have become more intensive, as cattle moved from being raised purely in range situations and as producers learned that they could effectively transport cattle from one location to another. Of course, environmental conditions and the presence of a multitude of pathogens have always and will always be factors to contend with.

Over the years and through research and practice producers and livestock professionals have developed an extensive array of drugs and pharmaceuticals to aid in combating disease and infection. Over time though, they have also discovered that in order for these tools to be truly effective, the animal's immune system has to be reasonably 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 the nutritional plane the animal is on and the availability of the components needed.

On another hand, 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 consumers 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. The one thing research has shown us is that improving the overall nutritional plane that an animal is on will, in general, improve it's performance and overall healthfulness. This is true regardless of whether the animal is in a pasture or confined stage of production.

Opportunities for Application

In this context we will only be able to review a few of the possibilities for the use of nutriceutical compounds but first we need to distinguish the categories they fall into. The first are basic nutrients. This would include nutrients such as protein, fat, fiber, minerals and vitamins. Probably 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, direct-fed microbials or probiotics. A third category could also be included that could be viewed a little more skeptically and that would include any of a host of �natural� products and could be described as herbs, or other organically based substances. The problem here is that most of the data for these types of products is anecdotal and not a lot of structured, refereed research and reporting has been produced. Our focus here will be on those materials that have significant research and investigative backing.

Nutrient Applications

As mentioned previously 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 some field trials have shown decreases in Bovine Respiratory Disease (BRD) morbidity rate with supplementation. An important note in cattle of this type is that formulation of receiving diets should take into account decreased feed intake by highly stressed, newly received beef cattle and known nutrient deficiencies. Also, it must be noted that the results shown have not been 100 percent conclusive and that fortification of such diets with trace minerals beyond the levels needed to compensate for these effects is difficult to justify in some instances.

Let's take a look at some specific examples:

As we noted in the last issue, 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. The absorption of the metal 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 be manifested 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. 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 roles of Se include 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 Ohio State University researchers has shown that supplementation with vitamin E decreases the incidence of mastitis, 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 be they yeasts, bacteria or fungi which are 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. There is a renewed interest in year-round or extended grazing to reduce the feed cost of cow-calf production programs. Yeast products may assist in digestion of forages.

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. In addition to these studies, research focused on monogastrics (swine and poultry) as well as on very young ruminants have shown a positive effect on heath by applications of yeast strains that target the lower gut specifically.

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

Conclusions

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.