and marketing propaganda, the horse owner often becomes disillusioned .... Are there ingredients like molasses, apple flavor, licorice or others that enhance ... Another concern is how the supplement is to be fed relative to your current feeding.
Feed Additives, Nutritional Supplements and Nutraceuticals for Horses Robert J. Van Saun, DVM, MS, PhD Department of Veterinary and Biological Sciences Pennsylvania State University Introduction A myriad of nutritional products are available to the horse owner for supplementing the diet offered to their horse(s). The most commonly available feed supplements are the commercial mixed concentrate products that blend various amounts of cereal grains, byproduct feeds, protein and fat sources, mineral and vitamin premixes to balance out a forage-based diet. Similarly, a wide variety of free choice or top dressed mineral and vitamin supplements are available. Products are marketed around specialized ingredients, specific horse activities, forage program and a plethora of other factors and anthropomorphized concepts. With so many different choices and marketing propaganda, the horse owner often becomes disillusioned and uncertain about what should be fed. Often times products are fed more in line with the owner’s perception of feeding practices rather than product-based feeding directions. This approach can often lead to nutritional problems. How does one determine which product is appropriate or correct for their horse and situation? This is a question I attempt to answer almost every week from some concerned and very confused horse owner. The first objective of this presentation is to clarify roles of feed supplements for horses and provide guidance on how to make objective comparisons between products for you clients. Secondly, I will tread into unchartered and murky waters of feed additives and nutraceutical products for horses. Beyond feed supplements supplying essential nutrients to balance a diet to meet daily nutritional needs, many nutritional supplements available for horses cross into the realm of feed additives. Feed additives are regulated by the Food and Drug Administration (FDA) and fall into one of two categories (FDA, 1992). Food constituents that are not intended to provide essential nutrients can be categorized as either substances imparting a technical effect on feed characteristics or affecting animal structure, performance or health. The latter category is legally defined as a drug by the FDA and thus requires extensive documentation of safety and efficacy. Because of the associated costs in product testing, many feed additives are being marketed as nutritional supplements having medicinal or therapeutic claims. These products are being termed “nutraceuticals” and currently attempt to occupy a “gray zone” relative to legal definitions (Boothe, 1997; 1998). A second objective of this presentation is to provide an overview of feed additives and nutraceutical products relative to horse nutrition and summarize available information applicable to making a decision for their use. Understanding Nutritional Supplements: Becoming a Better Consumer Most forage and grain ingredients fed to horses do contain some amount of all essential nutrients, but actual concentration is extremely variable between feed ingredients. Forages, especially grasses, may not be solely capable of meeting energy or protein needs. Additionally, forages are variable in their mineral and vitamin content both between and within forage types. Mineral content of a plant is dependent upon many factors including: plant species, stage of
maturity; cutting; season; soil conditions; fertilization; water availability; harvesting technique and storage practices. There are also certain chemical compounds in plants (e.g., phytates, oxalates) that inhibit dietary mineral (i.e., calcium, phosphorus and zinc) availability to the horse. Northeast forages do not meet suggested requirements for many minerals, but most especially selenium, copper and zinc. If you are feeding alfalfa hay you are most likely overfeeding calcium and protein. Phosphorus supplementation may be required when feeding some alfalfa or grass hays, but is excessive if cereal byproducts are fed. Salt is always supplemented in the diet. Of concern is the observation that forage potassium and iron concentrations are excessive compared to requirements. Both vitamin A and E are found in high amounts in pasture and these values are greatly reduced in hays, especially if they have been stored for any period of time. Typically, the majority of the fat-soluble requirement is provided in the diet as a supplement with very little expected to come from the forage as a result of the high degree of variability in forage vitamin content. So, how does one decide on the right supplement? When this question is asked, most often the person is looking for a simple answer; a single supplement that is “perfect” or right for every situation. There obviously is not a single right supplement. First, supplements need to complement the forage type and composition being fed. Few horse owners routinely analyze their forages stating they buy in small lots and that does not make it feasible to have forage analysis done. With this limitation, ask where the forage was purchased and obtain some description of the forage quality. This provides some basic insight into the potential mineral content of the forage based on many previous forage analyses collected throughout the Northeast (refer to feed library at www.dairyone.com). The following are some criteria by which you can help guide the horse owner in being able to compare and evaluate whether a supplement is appropriate for their feeding situation. To apply these concepts one needs to understand and interpret available information on product feed tags or labels. 1. Match supplement nutrient content to forage nutrient deficiencies. To achieve the overall goal of balancing dietary nutrient content to meet the animal’s needs, it is imperative that a supplement be appropriately matched to the basic forage program. This minimizes the potential for over supplementation problems, which may be as much of a potential danger as under supplementation. The difficult part here is interpreting and comparing nutrient concentrations of differing products based on label information. This can be a difficult task. You do need to compare apples with apples. Therefore you must carefully read the label information and convert the information to a equivalent basis for comparison. For example, nutrient content of a product may be presented on a per pound basis, per ounce basis or per dose basis. These are not necessarily the same for all products. Table 1 shows some basic conversion factors which might be helpful in comparing label values. Start with the guaranteed analysis on the product label. The completeness of the information for a given product is highly variable. Be careful of products that only show the minimal values, crude protein (minimum), crude fiber (maximum) and crude fat (minimum). These products may need to be sampled and analyzed to make any reasonable assessment. However, if little information is presented, it usually suggests something is being hidden. Using a Pearson Square (ext.colostate.edu/pubs/livestk/01618.html; prechel.net/formula/pearson.htm) one can calculate the percent of the diet the supplement must be to meet a desired nutrient dietary
concentration. Compare this value to the feeding directions on the label to see if there is agreement. Also determine if this feeding level is going to be acceptable to the horse owner. In many cases, required intake either exceeds or is below what is needed to balance the diet for a given nutrient. Additionally, not all nutrients within a supplement are balanced to the same level of expected intake. 2. Minimize over supplementation of any nutrient
Table 1. Common nutritional conversion factors.
Units Given
Units W anted
Conversion
oz
grams
multiply by 28.4
lb
grams
multiply by 454
lb
oz
divide by 16
grams
mg
move decimal to right 3 places
mg
grams
mg
:g
mg/kg
ppm
mg/kg
mg/lb
mg/kg (ppm)
%
%
mg/kg (ppm)
move decimal to left 3 places move decimal to right 3 places same value multiply by 0.454 move decimal to left 4 places move decimal to right 4 places
Many owners get into a mode that if a little is good then a lot is better. This is not necessarily the case. Mineral and vitamin toxicities are just as much a problem as deficiencies. Beware of products containing extremely high concentrations of a nutrient. Of greater concern is the compounding of multiple supplements. I have seen more nutritional problems with horses that will be fed multiple supplements. Some supplements highlight one or more nutrients and provide an excessive amount relative to defined requirement. A good example is kelp-based products, where they are touted as having high trace mineral availability, but they come with very high iodine content (>400 ppm). I have seen a number of cases of iodine toxicity in pregnant mares resulting in congenital birth defects in their foals. 3. Assess source and bioavailability of the nutrients within the product. Label nutrient content says nothing relative to the availability of the nutrient to the animal. A product may have a high concentration of a nutrient, but it may not be biologically available to the animal. One should review the ingredient list on the label to assess sources of nutrients. The ingredient list, by state feed code regulations, should list all ingredients from highest to lowest incorporation rate on an as fed (not dry matter) basis. However, collective names can be used such as plant or animal protein products, forage products, processed grain byproducts, among others (AAFCO, 2005). These collective terms are often used to allow for least cost formulation and potentially include lower quality ingredients. Also watch for multiple variations on a single ingredient being used to either mask the high incorporation rate, or to make it seem like another ingredient has the highest incorporation rate. For example, corn may be listed as whole, ground and cracked. This could result in corn accounted for the greatest percent
of the total feed, but not listed as the first ingredient as it is split among the different processed sources. Identification of mineral sources within the ingredient list is also of interest. Inorganic mineral sources include chloride, sulfate, carbonate and oxide forms. Within the inorganic forms, oxides have the lowest availability while sulfates generally have the highest. Organic forms of a mineral are generally considered more available than are inorganic forms. However, this varies with the specific type and source of organic mineral. Some organic minerals may even be less available. Read the ingredient list and see if all the minerals are in inorganic or organic forms and identify the order in which they are listed. If inorganic sources are listed before organic sources, this would suggest a greater proportion of the mineral is coming from the inorganic source. 4. Assess palatability of product. Palatability is the desire to consume a given feed product. Certainly supplements need to be palatable in order that they be consumed adequately. Visually inspect, smell and taste the product. Are there ingredients like molasses, apple flavor, licorice or others that enhance palatability? High fat products, which are becoming more popular, are of a concern relative to oxidation inducing fat rancidity and subsequent poor intake. Be sure high fat products have antioxidant protection and appropriate packaging to minimize rancidity. It does not matter how well balanced and formulated a product is if the horse will not consume it in adequate amounts. The only true test is to determine if the horse will eat it. 5. Practical feeding method within your feeding program. Another concern is how the supplement is to be fed relative to your current feeding program. If it is a top-dress, can you do it? If required, can the supplement be fed to individuals? Top-dressing a fine ground particle on hay is not appropriate. Free-choice supplements are convenient; however, their intake is based on salt ingestion. If the horse is receiving sufficient salt from other sources, i.e., forage, grain or plain salt, then additional consumption of a saltbased supplement will be limited. There is much individual variation in free-choice supplement consumption between animals, thus not assuring adequate intake on a daily basis. Free-choice supplementation is actually a poor method of insuring that sufficient nutrients are being consumed; however, it may be the only method if you can not top-dress on some concentrate. 6. Daily feeding cost of supplement. This may be the most important factor to consider. Many of these supplements are extremely costly as a result of specialty ingredients (e.g., chelated minerals) or nutrient content. Do not necessarily equate high quality with higher cost. Some of these products may cost you $0.50 to more than $2.50 a day to feed depending upon the type of product. That is equal to $180 to more than $915 per year for just the supplement! You had better be sure you are getting your monies worth! However, unlike the economically based thinking in feeding production animals (Hutjens, 2003), most horse owners are not necessarily worried about cost. Similarly, supplements used in agricultural animals must show a response, whereas many equine owners don’t ask what will it do as much as they as “will it do any harm”? The risk is more in obtaining
that fine edge, rather than determining an economic return. With individual animals it is difficult to actually measure a response as compared to a group of production animals. Improved performance in an athletic horse may mean reducing time by 1/100th of a second. This difference would be immeasurable, yet may make an enormous financial difference. Other Feed Additives and Nutraceuticals As previously described, there are two general categories of feed additives that may be incorporated into horse foods. The first category was non-nutritive food constituents that impart some technical effect on feed characteristics. These substances can enhance physical characteristics, stability and suitability of a feed product during manufacturing, processing and storage. Examples of such substances include antioxidants, colors, flavors, anti-caking agents, preservatives and pellet binders. Specific examples might include bentonite as a pellet binder, or mineral oil as a dust reducer. More often than not, horse owners see these substances listed on a feed label and question the appropriateness of their inclusion; thinking of them as more of a contaminant. These non-nutritive substances are either considered generally recognized as safe (GRAS) status or permitted food additives by the FDA. By legal definitions, GRAS substances are not considered food additives as permitted food additives must have extensive scientific documentation of their safety and efficacy. Essentially all supplements available for horses will have one or more of these non-nutritive substances incorporated to improve overall feed quality. The other category is the true feed additives or those substances, nutritive or nonnutritive, that are or become incorporated into the feed and are expected to impart some effect on animal health, structure or performance. It is this claim that brings about the controversy surrounding “nutritional supplements” or “nutraceuticals”. Under the current laws and interpretations by the FDA, any substance incorporated into food with the intent to alter animal health, structure or function is considered a drug (Benz, 1996; FDA, 1998). Using the legal definition of a drug the substance must undergo extensive evaluation for efficacy and safety, funded by the interested party, before being permitted for use as a food additive. The most obvious example is that of antimicrobial agents used for disease prevention or improved animal performance. However, this definition includes essential nutrients incorporated into the diet at amounts in excess of that defined necessary to prevent nutritional disease or other compounds known to have a vital role in metabolism, but not currently recognized as essential. Much interest exists relative to the role of nutrition on health and performance across species, especially in human nutrition. Because of the demand for accessability to nutritional supplements, in-spite-of safety or efficacy documentation, the US Congress passed the Dietary Supplement Health and Education Act (DHSEA) to permit such use of dietary supplements without the expensive documentation of safety or utility. However, relative to concerns for food safety in the human food chain, the FDA determined that DHSEA does not pertain to nutritional supplements intended for animals (FDA, 1996). Essentially no distinction is made between foods for companion animals versus animals that would enter the human food chain. This has been a contentious issue relative to companion animal and equine foods, as they are perceived not to enter the human food chain, though there are cultural differences in this distinction. With financial backing and recognition of tremendous market potential, there is a movement advocating use of nutritional supplements for non-human food chain animals, primarily dogs, cats and horses (refer to www.nasc.org).
Marketed food additives for horses includes products like antioxidant mixtures, direct fed microbials (probiotics and yeast extracts), sea kelp, herbs and botanicals, single-cell protein supplements, various joint supplements (glucosamine, yucca, chondroitin), fatty acid supplements and the list goes on. For the most part these are not products which are supplying some essential nutrient, but are being marketed as products which may facilitate or improve animal performance, health or other facet. In this regard they would be considered a “drug” by the FDA and warrant research to validate efficacy and safety. However, most of these products do not undergo strict evaluation as they are being marketed as nutritional supplements. One of the primary concerns in the lack of regulation of nutritional supplements beyond safety is the tremendous variation in quality control and content of active ingredient. A number of studies have shown many nutritional supplements not to contain as much active ingredient as was listed on their label. In evaluating these nutritional supplements use the 4 R’s criteria as follows (Hutjens, 2003): • • • •
Response - What is the effect expected from this product? Research - Is the product backed by nonbiased studies? Results - What are the results with your animal? Returns - Is it economically beneficial to use this product?
If you can not adequately answer all of these questions to your satisfaction then you may not want to be using that given supplement. The bottom line with most of these supplements is that you need to become a more aware and informed consumer. Do not be afraid to ask questions and request information pertaining to the product. Do good comparison shopping with supplements. The reason there are so many supplements available is the fact that money can be made from their sale. Table 2 provides some very basic summary information about a number of the mainstream feed additives being used in equine nutrition. For the most part there is little scientific data documenting response to these products in horses. This information can be used to help your clients make some decisions relative to product usage. Summary There is an appropriate place for supplements in the equine feeding program especially in light of the fact that most forages do not adequately provide sufficient essential nutrient supplementation alone. However, supplements should matched by nutrient content to the basic feeding program and not visa versa. One should be careful not to over supplement any one nutrient to prevent toxicity problems. Compounding of multiple supplements is a dangerous practice as a result of potential over supplementation problems. Once a supplement having an appropriate nutrient content has been identified, further evaluation should be based on ingredient sources, palatability, feeding method and cost. Choosing an appropriate mineral-vitamin supplement is greatly facilitated by forage analysis if feasible. Use of nutritional supplements is common place in equine nutrition, in-spite-of the shaky legal grounds for their use. Most owners are going to feed these supplements in an effort to gain that “competitive edge”. You as the veterinarian should at least become familiar with the evidence behind use of such products in order to help your clients make an informed decision. Nutritional assessment and consultation are opportunity areas open to practitioners in working with their equine clientele.
Table 2.
Description of some feed additives or supplements with animal performance claims and documented research in horses and associated costs.
Additive Type
Examples
Expected Actions
Research Support/Status A significant number (>50) of published controlled studies addressing various aspects of antioxidant effects. Study results have been mixed, but most suggested of some positive effect.
Antioxidants
Vitamin E & Selenium; Vitamin C; Grape seed extract; lipoic acid
Minimize oxidative damage to reactive oxygen species generated during intense exercise or inflammatory conditions
Antimicrobials
Antibiotics; Anthelmintics
Provide therapy or prevention of specific Products are highly regulated by FDA pathogen associated diseases and must be used accordingly
Daily Costs1
$0.33-0.99
$0.63-0.85
Other than some uncontrolled clinical reports in alternative therapy journals, there is little scientific documentation. Tremendous problems in active ingredient documentation and potential for toxicities. One study showed garlic intoxication.
variable
Botanicals and Herbs
wide range of whole plants or Insect control (garlic); calming effects; extracts antiinflammatory; metabolic effects
Enzymes
Phytase; Cellulase; Hemicellulase
Improve digestive capacity of specific compounds, nutrients within consumed diet
Small number of studies (
