Water is the most simple element in equine nutrition, yet remains the most important. Adequate hydration is necessary for circulation and transport of nutrients as well as being an essential part of the metabolism of energy, protein and minerals. The horse uses this store of water and electrolytes during work. Without adequate body fluids, the function of the many body systems is disturbed: The horse has a digestive system very different from ruminants (i.e. cattle). The horse has a small stomach (2-4 gallons) capacity with a large hind gut which is important in water transport. Recent scientific studies indicate that particle size of ingesta in the gut of the horse may play an important role in water-holding capacity. This factor may be significant in the ability of the horse to tolerate periods of reduced water intake. The irregular access to water in the backcountry makes it important that our consideration of foodstuffs maximize natural water retention. Forages provide maximum particle size as compared to cereal grains. Thus, rations with maximum roughage are important in combating dehydration on back country trips. Horses should be allowed time to drink whenever possible to maintain adequate water reserve in the gut.
ELECTROLYTES-MINERALS
Electrolytes - elements such as sodium, chloride, potassium, calcium, phosphorus and others are present in all body fluids. These elements are essential in muscle and nerve function. Reduced levels of electrolytes are associated with disorders such as myositis (tying up) and thumps. Salt is the natural source of sodium and chloride and should be provided for stock on extended backcountry trips. Large salt and fluid loss occurs from sweating (4 gallons/hr.) during heavy work. These losses may not be replenished in adequate amounts by some rations. Alfalfa is high in calcium and potassium; while cereal grains are high in phosphorus. A total cereal grain diet in the backcountry may lack adequate electrolytes for maximum muscle function and energy metabolism. The use of supplemental electrolytes is of benefit, but the correct balance of these elements is most important. A simple electrolyte solution is one containing 1 level tablespoon of table salt (NACI) and 1 level tablespoon lite salt (KCI) in 1 gallon of water. Concentrated electrolyte solutions or pastes are actually contraindicated in dehydration. Adequate water must first be available before electrolyte supplements are considered.
PROTEIN
Protein requirements can increase during prolonged work. The adult horse requires about 8-10% protein in its ration. Alfalfa hay is a good source of protein (14-16%) depending on maturity and method of harvest and storage. Good grass or oat hay may have 6-8% protein. Corn is low in protein (i.e. 6-8%), while good quality oats or barley may have 10-12%. Extended trips in areas of limited forage will require consideration of protein levels in feed.
ENERGY
Energy is provided by both roughage and cereal grains; however, in different forms. This energy is utilized differently, according to the foodstuff. Roughage provides energy in the form of cellulose, which requires microbial digestion in the hind gut for utilization. Cereal grains provide energy in the form of starch, which is digested more rapidly in the gut and is available soon after ingestion. Peak levels of blood glucose occur within 2-3 hours of cereal grain feeding; whereas, energy levels from roughage peak more slowly, but are more prolonged. Thus, the type and duration of work will determine the type of feed and when best fed for optimum benefit.
Energy levels (as measured in calories) in feeds can be another consideration when available forage or regulations require packing feed. Good quality alfalfa hay has about 1,000 Cal./lb.; grass hay 800 Cal.lb.; oats 1200 Cal./lb.; and corn 1600 Cal./lb.
Estimate of energy requirement in the horse:
ROUGHAGE
The horse has a minimum roughage requirement for normal digestion. This has been estimated at 1% of body weight (i.e. IO lbs. for the 1,000 lb. horse). The roughage requirement takes into consideration particle size. Finely ground roughages, such as those found in some pelletted rations, may be lacking adequate particle size for optimum digestive function and water retention. If natural forage is available, it may require 6-8 hours for gazing for the horse to gather this roughage requirement. Some regulatory agencies require only processed feeds in the backcountry for noxious weed control. When we pack processed rations, we should consider the horse's roughage requirement.
IN GENERAL
Horses can vary in their nutritional requirements. We all recognize the "easy keeper" and the "hard keeper." Age, physical condition and body frame are other factors which may influence nutrition requirements.
A simple formula of 1-2-3 may also be used to estimate feed requirements. 1% of body weight for roughage requirement; 2% of body weight for roughage requirement, maintenance and light work and 3% of body weight for roughage requirement, maintenance and heavy work.
Most horses will eat about 2% of their body weight daily. When heavy work requires a large number of calories, the horse may not be able to eat enough roughage to satisfy his total caloric requirement. A combination of high energy cereal grains and roughage is necessary to satisfy the nutrient demand.
Good nutrition for backcountry saddle and pack stock combines common
sense, experience and the art and science of feeds and feeding.