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Feeding Forage: Choosing Which Hay or Chaff to Feed Your HorseBy Dr. Peter Huntington · May 28, 2012

While there are some differences between forages, they all serve the same purpose of being vital fiber sources for the horse. If you are fortunate enough to have a choice of forages, the decision of which to feed should be based on what you are trying to achieve with the horse. The major differences between a grass forage (including oaten and wheaten chaff) and a legume (lucerne/alfalfa and clover) are energy, protein, and calcium content.

Energy Content

Fiber found in forages is digested by the microbial population of the hindgut to produce energy for the horse. There are forms of digestible fiber and indigestible fiber found in any plant. The higher the percentage of digestible fiber and the lower the indigestible fiber, the more energy there is in that forage. There tends to be more digestible fiber in the leafy portion of the plant and more indigestible fiber in the stem. Therefore, a forage with more leaf and less stem will give the horse more energy. Lucerne/alfalfa that is harvested at the right time and handled carefully after harvesting will have a lot of very digestible leaves with some stem, and thus it is very high in energy. A poorly made lucerne/alfalfa will have more stem than leaves and will contain less energy. The same goes for the harvesting of grass hay: the earlier in its growth it is harvested, the more leaf it will have and the better quality it will be.

By looking carefully at grass hay, the amount of leaf to stalk (stem) will dictate the quality of the hay and its energy content. With oaten chaff, it is obvious that there is almost no leaf to be found and almost all stem. The amount of indigestible fiber is much higher in oaten chaff or hay than in most types of lucerne/alfalfa, which means that the amount of energy a horse can get from it is lower. However, early-cut oaten and wheaten chaff or hay can contain a lot of sugar, which makes them very palatable and increases the energy content. Indigestible fiber does serve a purpose in the horse as it keeps the digesta moving through the digestive tract. Too much indigestible fiber increases the risk of impaction colic and reduces the energy supplied by the hay. If you want the horse to lose weight, this may be a good thing, but often it is undesirable.

It is possible, therefore, to manipulate the amount of energy supplied to the horse with the use of different forages. If a horse has difficulty keeping weight on, adding more lucerne/alfalfa to the diet may be warranted. If you have a horse that is an easy keeper, lucerne/alfalfa may not be a wise choice.

Use caution when making changes in the fiber sources for the horse. The microbial population in the large intestine is very sensitive to changes in the different fiber types and takes a while to adjust to a new type of forage. One of the biggest shocks for the microbes is going from grass to legume hay. During the time when the microbial population is trying to adjust to the legume, it may produce more gas or not digest the forage well. The result may be a horse with a lot of gas, possibly mild gas colic, or the horse may have loose or runny manure. Making any changes in the quantity of legume or grass forage should be done gradually.

Protein Content

The protein content of legumes (lucerne/alfalfa and clover) is much higher than that of grass forages. Lucerne may have anywhere from 16 to 20% protein, while grass may only have 4 to 12% protein, depending on the quality of the hay. In general, the protein in lucerne/alfalfa is in excess of the requirement of the horse, and grass hay or oaten chaff may be just right or too low to meet the requirement. If you are feeding poor-quality forage, you may need to increase the protein content of the diet. Adding some lucerne/alfalfa will increase the total amount of protein and improve the quality of the diet. This may be particularly important for the young growing horse or lactating mare, where a deficiency in protein will limit growth or milk production.

Excess protein in the diet can be broken down to be used for energy. Some of the drawbacks of using protein for energy are cost, increased thirst, and increased urine output. The smell of the urine can be very strong because of the excess ammonia produced during the breakdown of protein, and this may be irritating to the lungs of the horse in the stable or the person who has to clean the stall.

Calcium Content

Legumes are higher in calcium than grass forages. This can be an advantage or a disadvantage depending on the other ingredients in the diet. In general, the calcium content of lucerne/alfalfa is in excess of the requirement of most horses, but if fed in small quantities will not increase the amount of calcium in the diet to excessive levels. Excess calcium is disposed of by the kidneys through the urine. Horses eating large amounts of lucerne/alfalfa will have thicker, chalky whitish urine because it is full of calcium.

Calcium and phosphorus are strongly linked in their functions in the body. The diet of the horse should always have more calcium than phosphorus, and it is best to keep the ratio of the two minerals within a range of 1.5-3:1, calcium to phosphorus. Grains or grain by-products are very high in phosphorus, so a diet with a high grain or by-product content may adversely affect the calcium-to-phosphorus balance. Having lucerne/alfalfa in the diet will increase the calcium intake and may help balance the phosphorus. This is true for straight grains, but commercial mixes usually have added calcium and are already balanced for calcium and phosphorus. Another circumstance in which the calcium from lucerne/alfalfa is valuable is for horses grazing high-oxalate tropical pastures. In these grasses, oxalates bind calcium and reduce its digestibility, thus creating calcium deficiency that can lead to bone weakness and nutritional secondary hyperparathyroidism, also known as “big head disease.” Kikuyu is a common high-oxalate grass, but a number of other tropical grasses can lead to this problem.

In conclusion, adding lucerne/alfalfa or clover to the diet can be helpful in certain circumstances, depending on the goals trying to be achieved. Fear of using lucerne/alfalfa is unjust; it is merely a question of understanding the differences between it and other forages. There are many horses around the world that live on lucerne/alfalfa as the only source of forage because of the unavailability of any other type and do very well. It’s about feeding a balanced diet for the horse and the choice of hay or chaff to feed will vary according to individual circumstances.