Lucerne Hay in Equine DietsBy Dr. Peter Huntington · April 15, 2011

There are some differences between lucerne (alfalfa) and grass hay or oat chaff, but they all serve the same purpose of being vital fibre sources for horses. If you are fortunate enough to have a choice of forages, the decision of which type to feed should be based on what you are trying to achieve with the horse.

The major differences between a grass type forage (including oat and wheat chaff) and a legume (lucerne and clover) are energy, protein, and calcium content.

Energy

The fibre found in forages is digested by the microbial population of the hindgut to produce energy for the horse. There are forms of digestible fibre and indigestible fibre found in any plant. The higher the percentage digestible fibre and the lower the indigestible fibre, the more energy there is in that forage. There tends to be more digestible fibre in the leafy portion of the plant and more indigestible fibre in the stem. So, forage with more leaf and less stem will provide the horse more digestible energy.

Lucerne 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 will have more stems than leaves and will have 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.

Looking carefully at grass hay, the amount of leaf to stalk (stem) will dictate the quality of the hay and its energy content. Looking at oat chaff, it is obvious that there is almost no leaf to be found and almost all stem. The amount of indigestible fibre is much higher in oat chaff or hay than in most types of lucerne, which means that the amount of energy a horse can get from it is lower. However, early cut oat and wheat chaff or hay can contain a lot of sugar, which makes them very palatable and increases the energy content.

Indigestible fibre does serve a purpose in the horse, as it keeps the digesta moving through the digestive tract, like a laxative, which is also important for the health of the horse. But too much indigestible fibre 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.

Horse owners can manipulate the amount of energy they are supplying the horse with the use of different forages. For a horse that is difficult to keep weight on, adding more lucerne to the diet may be warranted. If you have a horse that appears to stay fat on air, lucerne may not be a very good idea.

A word of caution about making changes in the fibre sources of the horse: The microbial population in the large intestine is very sensitive to changes in the different fibre types and takes some time 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 a little gas colic), or loose or runny manure. Making any changes in the forage portion of the diet should be done gradually.

Protein

The protein content of legumes (lucerne and clover) is much higher than that of grass forages. Lucerne may have anywhere from 16 to 20% protein, while grass hay may only have 4-12% protein, depending on the quality of the hay. In general, the protein in lucerne is in excess of the requirement of the horse, and grass hay or oat 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 will bring the total amount of protein up and improve the quality of the diet. This may be particularly important for the young, growing horse or lactating mare, in which 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 urination. 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 or caretakers in the stable.

Calcium

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 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 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 1.5:1 to 3:1 (calcium:phosphorus). Grains or grain byproducts are very high in phosphorus, so a diet with a high grain or byproduct content may adversely affect the calcium:phosphorus balance. Having lucerne 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 where the calcium from lucerne is valuable is for horses grazing high oxalate tropical pastures. 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”). Kikuyu is a common high-oxalate grass in tropical areas, but a number of other grasses can lead to this problem.

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