Ask The Equine Nutritionist

I bought your nutrition book, and I find it very informative and helpful. However, I do have one question. In the book, you refer many times to "a high quality protein source." What exactly do you mean by that? I mean, I know that it is the essential amino acids, but what contains these? I've looked through the book several times, but I didn't find what a quality protein source IS. If I've missed it, I'm really sorry!

I know there are several commercial products that are called ration balancers that are said to have high quality protein, and I know that you make one also. Are these commercial products the only source of essential amino acids?

Does whole flax seed contain essential amino acids, as well as the essential fatty acids? What would be some other, non-manufactured sources?

A high-quality protein source is defined as one whose amino-acid profile most closely matches the amino-acid requirements of the animal. This a very indistinct and hard to define thing which is why it is rarely used.

In humans high-quality protein usually means proteins of animal origin such as meat, fish or eggs. But horses cannot be fed these things, so we have to look at the vegetable protein sources. Most vegetable protein sources are going to be lower in essential amino-acids than animal sources and there is a degrees of 'quality' among the various vegetable sources. Thus for horses high quality protein sources are things like Pulses, e.g soy beans, field peas or field bean and legumes such as alfalfa or clover. The legumes provide a less high quality protein source than the pulses.

Another source of high quality protein for horses are the oil seeds such as flax seed, sunflower seed or canola. If the oil seeds have had the oil removed what is left is the protein and fiber part and so the extracted meal from the oil seed is often higher in protein than the original plant. Many oil seed meals are used as 'high quality' protein sources for horses and other livestock. The use of the words 'high-quality' here is purely subjective, there are few if any who can tell you the amino acid profile of any given oils seed meal. Examples are things like soy bean meal, canola meal, cotton seed meal, peanut meal, etc.

Occasionally people use an animal source of protein such as milk powder or eggs to raise the protein quality for horses. Both milk and egg powders good sources, and are truly high quality proteins, but must be fed in limited quantities, plus they are very expensive. For horses do not feed any kind of meat based protein source like meat meal .

Balancer pellets may or may not contain essential amino acids, it depends on the ingredients used to make them and they are very variable. You might need to ask the manufacturer which amino-acids the product contains and in what amounts. The ones to look for are Lysine (Lys), Methionine (Met), Tyrosine (Tyr), Threonine (Thr) and maybe Tryptophan (Trp).

The proteins found in flax seed do contain some essential amino-acids, not a perfect match for the requirements of the horse, but better than say alfalfa or peas.

Dr. Melyni Worth Ph.D. - 2004 (c)

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