Nutrient requirements, feed formulation and environmental constraints: a new focus is needed in the equine industry

Published on: 10/20/2006
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The last update of the National Research Council’s publication ‘Nutrient Requirements of Horses’ was published in 1989 and contains data from studies published through 1988. A number of trials have been conducted in the past 14 years that add significantly to that body of literature. Additionally, the focus of nutritionists worldwide has changed with increasing concerns about the impact of animal feeding on the environment. With new regulations on animal feeding operations about to be put in place, the mantra has shifted from ‘maximum’ to ‘optimal’ formulations. The equine industry will not be immune to those changes; and we must begin to look for new ways to meet the nutrient requirements of horses in a more environmentally friendly way while improving the health and well being of this majestic animal.

Horsemen want to do the best job possible in feeding their animals. No one wants to feed a diet that prevents a horse from performing to its genetic potential. The challenge lies in knowing what is ‘best’. Diets today are generally over-formulated, often with marketing the driving force with little regard for whether the horse actually needs the higher nutrient levels. For example, how many commercial diets these days contain less than 50 ppm copper? The 1989 National Research Council publication lists the copper requirement for all horses at 10 ppm. Are there sound scientific principles that suggest we should be adding more? The same case exists for zinc, calcium, phosphorus and manganese. Is the over-formulation really necessary? Are we truly helping the horse or simply placing an unnecessary burden on the digestive system and kidneys and harming the environment with excess minerals that represent potential pollutants to water supplies and soil profiles?

Excess dietary protein presents a similar problem. Horsemen have a propensity for feeding excess protein, particularly in the case of performance horses. There is no scientific study that suggests a need for higher protein concentration in the diets of exercising horses. We are not even sure if an increase in requirements for specific amino acids actually exists for performance; but protein level remains a focal point for horse owners purchasing feed. The first question asked at the feed store is “What is the protein level?”. When one considers the increase in the amounts of feed needed to meet the energy requirements for exercise, the protein ‘level’ should actually be lowered, not raised. The excess nitrogen, which must go somewhere, becomes an entirely unnecessary potential pollutant. Fortunately, horses represent only a minor portion of all the animals consuming and excreting environmentally-active compounds, but we must work toward minimizing the impact of our passion.

Here are three situations the industry must address.


In terms of precise nutrient requirements for specific functions, there is much we do not know. The equine research community must undertake a serious scientific effort to precisely define the nutrient needs of horses, particularly with respect to protein and mineral requirements for growth and exercise. Protein and mineral recommendations in the current NRC publication are based on limited data and therefore have been subject to suspicion and in some cases outright ridicule by both the scientific and feed industry communities. What is known about the basic absorption mechanisms and factors affecting them is minuscule compared to information available for other species. A crude protein standard will simply not allow nutritionists to formulate diets that precisely meet the needs of all classes of horses. This type of research is not high profile and is difficult to sell to funding agencies. Adult horses will not likely die from a 25% excess or deficiency of phosphorus; and consequently the surveys of the horse-owning public used by granting agencies to determine funding priorities do not identify nutrition research as a high priority item. Nevertheless, the day is coming when these data will be critical to horse owners.

Research is needed on mechanisms and management strategies to maximize nutrient uptake and minimize the excretion of nutrients. Studies on the use of phytase, conjugated minerals, dietary cation-anion difference, urease inhibitors and a whole host of other management strategies need to be conducted immediately. There is a window of opportunity that currently exists for the industry to move forward regarding environmental issues. To date, the horse industry has managed to maintain a low profile with respect to new pollution control efforts, but that will not last. Horse farms will be identified by the EPA as sources of potential pollution as they have done for other livestock operations; and the industry must be able to demonstrate that it has already haven taken action to minimize the environmental impact of the horse and its use.

The NRC publication on Nutrient Requirements of Horses needs to be updated as soon as possible. Given the state of the federal budget, the general lack of political influence of the horse industry and low profile nature of nutrition research, it will take the efforts of scientists, horsemen, and the feed industry working together to raise the money necessary to bring this task to reality. The NRC’s Committee on Animal Nutrition cannot appoint a subcommittee and begin work until the money, approximately $300,000, is in hand or at least pledged.

Feed formulation

The feed industry must formulate and market diets  based on science. The use of new feed ingredients will likely be a part of this strategy. There are certainly ambiguities with respect to the requirements for certain minerals and the efficacy of organic mineral sources, but as new data are published that prove efficacy, it then becomes incumbent on both the feed industry and the horseowning public to adopt those changes, particularly when they result in higher retention and less excretion of those minerals.

Some have suggested, even stated, that diets formulated to NRC specifications just will not sell. While that may be true today, in the very near future it may be impossible to sell something not formulated to scientifically-based requirements. The liability associated with the gross overfeeding of protein and minerals will be a powerful incentive for both the industry and for horse owners.


Finally, horse owners must be educated on these issues. It is unlikely that many producers or consultants are even aware that a horse operation with 150 head of horses, confined for any 45-day period throughout the year, could potentially be regulated as a Confined Animal Feeding Operation (CAFO). That means that a Comprehensive Nutrient Management Plant for solid wastes must be devised, including a strict inventory of nutrients in and nutrients out, and that no runoff may be discharged from the premises at any time for any reason. Think of the impact on horse farms that pride themselves on their pastoral setting with a stream meandering through the middle of the farm. Whether that education comes from the Cooperative Extension Service, universities, private consultants or feed companies does not matter. The fact is that the waste products produced by feeding horses will no longer be looked upon as simply an on-farm nuisance. Owners will no longer be able to fill up the wash created by overgrazing a pasture with the manure and soiled bedding cleaned from the stalls. No longer will a 5-acre pasture be sufficient land area on which to dump the cleanings from 100 stalls per day. The responsibilities of horse ownership are going to become much greater as horse farms come to be viewed in waste management terms. If the industry is to continue to flourish, the scientific community, the teaching community and the feed industry have a big task in front of them.

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