Nutritional supplements in horses
What should practitioners consider when evaluating and recommending nutrient supplements for equine patients? In addition to looking at the traditional issues of an animal's age, activity level and general health, practitioners should also consider the nutrient's perceived benefits, efficacy and bioavailability.
Following is a look at nutritional supplements, including nutraceuticals, how they are and aren't regulated and the purported benefits of some of the supplements.
First, the basicsThe Nutrient Requirements of Horses from the National Academy of Sciences is the basis for evaluating nutrient needs of horses.1 Published in 2007, it provides a thorough review of the various classes of nutrients (e.g., energy, carbohydrates, protein and amino acids, fats and fatty acids, vitamins, minerals), including estimates of nutrient requirements for growth, maintenance, reproduction and performance. It also discusses water and water quality, feeds and feed processing, feed additives, feed analysis, ration formulation and evaluation and the nutritional needs of horses experiencing various disease states.
When feeding horses, management conditions are pivotal; environmental access to nutrients can influence the feeding management that's implemented. Horses that live outdoors with access to pasture are fed very differently from those in confinement.
In addition to the nutritional requirements responsible for sustaining normal physiology, nutrient expenditures associated with degrees of activity can influence feeding practices. Horses may be involved in high levels of performance (e.g., racing, polo, dressage, cutting and roping, ranch and farm work), as well as moderate levels of exercise. Horses at varying levels of exercise require different amounts of energy, as well as other nutrients such as electrolytes and water for intense physical activity and performance.1 Special considerations are also given to young and growing horses, breeding stallions and pregnant or lactating mares.
Horses may be fed fresh and stored forages; grain mixtures; processed grains compressed by rolling, flaking or crimping; pelleted grain mixtures; pelleted forage; textured feeds and extruded feeds (cubes, wafers, pellets). Rations are usually composed of ingredients that are processed after harvesting. Processing can affect the physical, chemical and microbiological properties of the feedstuff by altering the size, density, nutrient content and texture. Digestibility, utilization, intake and acceptance may also be affected.
Nutrient supplements defined
The Federal Food, Drug and Cosmetic Act [Title 21, Code of Federal Regulations §321(f)] defines feed additives and includes items that are intended or reasonably expected to become either directly or indirectly a constituent of food or that may alter the characteristics of a food. Additives also include substances intended for use in the manufacturing, processing, packaging and storage of a food. Animal diet feed additives may be non-nutritive ingredients that stimulate growth or other aspects of production, improve the efficiency of food utilization or benefit the animal's health or metabolism.
Numerous nutrient supplement compositions are available. Such supplements are often mixtures of vitamins and minerals, though some include ingredients not commonly part of the natural equine diet. These supplements may include botanicals, herbs, extracts, enzymes, metabolites and amino acids. They're sold in the form of tablets, liquids, pastes, powders and granules.
The American Association of Equine Practitioners (AAEP) endorses the 1996 American Veterinary Medical Association (AVMA) guidelines,2 including the use of nutraceuticals. The therapeutic use of micronutrients, macronutrients and other oral nutritional substances is permitted, though veterinarians should be aware of the ingredient content and their benefits, bioavailability, efficacy and safety.
While not applicable to animals, a dietary supplement is defined by the Dietary Supplement Health and Education Act (DSHEA) as one that "contains one or more of the following dietary ingredients: vitamin, mineral, herb, or other botanical, amino acid or dietary substance for use by man to supplement the diet by increasing the total dietary intake, or a concentrate, metabolite, constituent, extract, or combinations of these ingredients."3 Under DSHEA, dietary supplement manufacturers are responsible for ensuring a supplement is safe before it's marketed and providing a reasonable assurance that no ingredient presents a significant or unreasonable risk of illness or injury.
Manufacturers cannot claim their products prevent, treat or cure disease. Within the DSHEA, though limited in its ability to regulate products prior to marketing, the Food and Drug Administration (FDA) is responsible for taking action against any unsafe dietary supplement product after it reaches the market. Generally, manufacturers are not required to register their products with the FDA nor get the FDA's approval before producing or selling dietary supplements. Manufacturers must ensure product label information is truthful and not misleading. Unlike for human dietary supplements, the Center for Veterinary Medicine (CVM) has determined DSHEA doesn't apply to animals, animal feeds or to veterinary nutraceuticals.4,5
Animal dietary supplements
According to the National Research Council, an animal dietary supplement is defined as "a substance for oral consumption by horses, dogs and cats, whether in or on feed or offered separately, intended for specific benefit to the animal by means other than provision of nutrients recognized as essential or for provision of essential nutrients for intended effect on the animal beyond normal nutritional needs, but not including legally defined drugs."6
Nutrients and nutrient supplements are regulated by various agencies including the FDA's CVM and the individual states where the products are sold. Guidance for the state agencies is provided by the Association of American Feed Control Officials (AAFCO).5 AAFCO writes and revises model bills, which include food and drug regulations set forth in the Code of Federal Regulations and are often the basis of state feed regulations. The AAFCO official publication, published yearly, includes continuous revisions and additions to approved ingredients and animal feed additives. Recently, AAFCO took further action regarding nutraceuticals, establishing the Enforcement Strategy for Marketed Ingredients, which addresses unapproved ingredients and ingredients with unapproved claims.5
Some manufacturers have introduced animal products from their position within the human nutraceutical market. Many of these products have emerged in the horse market via a bridge from the human supplement market with the assumption that all species need the supplement sometimes without scientific data supporting its efficacy, bioavailability and nutritional purpose in horses. Equine practitioners should scrutinize those products before recommending their use in horses.
The National Animal Supplement Council (NASC), formed in 2001, is a nonprofit industry group consisting of manufacturers, suppliers, veterinarians, dealers and animal owners dedicated to protecting and enhancing the health of horses and companion animals. The group's aim is to place safety standards on animal supplements and on the manufacturers and to promote the use of safe ingredients in their products. The NASC Quality Seal Program is awarded to those manufacturers that meet the organization's standards (for more information, visit http://www.nasc.cc/).
However, NASC does not require companies to perform efficacy studies on their products or verify that scientific research data are available proving the products are effective for the benefit(s) they claim in horses.
Note, numerous reputable nutrient supplement companies are not members of NASC but do follow proper labeling and legitimate good manufacturing practices and have their products supported with scientific data showing their benefit and efficacy for use in horses.