Horse Feeding

 

General

The most significant difference in feeding horses as compared to other domestic livestock is the purpose for which they are used. The working horse must be regarded as an athlete. Unfortunately, there is very limited experimental information on the nutritional needs of the horse.

 

Digestive System of the Horse

  1. The upper part of the GI tract is similar to the monogastric
  2. At the lower end of the GI tract is its large fermentation organ, cecum (much like the rumen)
  3. Both the rumen and cecum contain bacteria that break down cellulose; however,
    1. Ruminants ferment feed at the beginning of the GI tract
    2. Horses digest cellulose at the end of the GI tract
  4. Ruminants and horses eat at different rates
    1. Ruminants can eat rapidly and “store” in the rumen for leisurely rumination later
    2. Horses must eat more slowly to not force feed through the GI tract too rapidly (before digestion is complete)
  5. Forcing feed through the GI tract too rapidly can cause undigested feed to enter the cecum, and starch residues will be fermented rapidly, causing excessive gas production

 

Digestive Physiology

  1. The horse is a nonruminant herbivore that utilizes a significant amount of microbial fermentation in the hindgut (cecum).
    1. This hindgut fermentation is primarily for fibrous feeds.
    2. The principle microbial inhabitants of the equine gut are similar to the rumen of ruminant animals.
    3. Therefore fermentation results in the production of CO2, CH4, and VFA (acetate, propionate, and butyrate).
    4. Methane production in the hindgut is less than in the rumen, and is equivalent to less than 3% of the total energy intake.
  2. VFA’s are readily absorbed in the hindgut.
    1. 30% or more of the energy utilized by the horse can come from VFA’s.
    2. Propionate can also result in a significant amount of glucose production.
  3. Fiber is not utilized by the horse as efficiently as cattle because horses have a faster rate of passage.
    1. Therefore the microflora do not have as much time to digest the fiber.
  4. Bacteria in the hindgut also produce protein and water soluble vitamins, but the utilization of these products is not efficient.
  5. It is important to remember that the horse needs to be fed, but also the microbes need to be fed as well.
    1. Proper feeding can reduce the incidence of colic and other digestive problems.
    2. The horse is a grazing animal, and therefore performs optimally when a slow steady supply of fermentable material is allowed for the microflora.
    3. Research has shown that feeding several times a day is best – especially when large amounts of grain are fed.  The same research showed that on a high energy, low fiber diet and fed twice a day, microbial activity was adversely influenced, and predisposed the horse to more spontaneous digestive disturbances.
    4. Therefore, when feeding grain, three or more feeding per day is recommended.
  6. Remember that dietary ingredients can influence microbial activity.
    1. High starch or grain intake decreases the relative amount of acetate production and increases the relative amount of propionate.
    2. Dietary changes should be made gradually to allow for proper corresponding microbial changes to occur.
    3. Abrupt changes in the horses diet can alter microbial population, intestinal pH, and kill certain types of bacteria which may lead to endotoxin release.
    4. It is suggested that the release of endotoxin is one of the causes of founder (or laminitis).
    5. It is recommended that forage be fed at 1 lb dry matter per 100 lb of body weight in order to maintain proper microbial activity.

 

General Nutrient Requirements of the Horse

  1. Horses can survive very well on pasture (when ample minerals are provided)
  2. Horses require energy like all animals, but the potential exists for energy intake to be problematic
    1. Normal Requirements, Mcal/d (BW and ADG in kg):

                                                               i.      Maintenance = 1.4 + 0.03BW

                                                             ii.      Weanlings = 1.4 + 0.03BW + 9ADG

                                                            iii.      Yearlings = 1.4 + 0.03BW + 16ADG

                                                           iv.      Long Yearlings = 1.4 + 0.03BW + 18ADG

                                                             v.      2 Year Olds = 1.4 + 0.03BW + 20ADG

    1. Energy for work depends on (4 to 16 Mcal per hour of work):

                                                               i.      Type of work

                                                             ii.      Speed of work

                                                            iii.      Terrain over which the work is done

    1. Obesity
    2. Founder (laminitis)