It really depends on what else you are feeding-what is the protein content of your hay and anything else they are getting? My foals-2 yr. olds are fed free choice alfalfa/grass hay that has 10-12% protein. I feed omelene 300 to them as well. I can't remember exactly what the percent of protein is for that..14 or 16. As yearlings they are very mature, filled out all around but not fat (well maybe just a little
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If you have good hay, 14% should be sufficient. Also make sure they are getting enough calcium for their growing bones! People forget about all the other stuff-if they don't have a well rounded diet, they will have a lower immune system which makes them more vulnerable to parasites and illnesses and they won't be able to utilize nutrients/vitamins the way that they normally would.
Here is a GREAT article about protein in an equine's diet-just part. I will post the link for anyone who would like to read it all.
PROTEIN ARTICLE
Protein, Praises and Woes
~ by Gretchen Topel, Equine Nutritional System
Protein is absolutely necessary for the body to survive, but an overload of protein will break down the tissues, organs, and structure of the body over time. Additionally, a horse that consumes too much protein will be at an even greater risk of contracting diseases and be predisposed to other symptoms such as hypothyroidism, tying up, kidney problems, and arthritis to name a few.
Without proteins, DNA, enzymes, and hormones would not exist as these substances are primarily composed of proteins. Imagine how out of balance a horse's body would be if they did not have enough protein! Some horses, but very few, do suffer from too little protein in the diet, but mostly, I find that if a horse is a having a severe issue, they are presently consuming too much protein in the form of alfalfa and/or a high protein grain formulation.
What is the ideal balance of protein in a horse's diet?
No mammal should consume more protein than what was available from his or her mother's milk. Mare's milk is 12% protein. Colostrum is higher in protein, around 18%, but drops to 12% for the duration of lactation. When the protein level of the total ration is increased beyond 12%, the body becomes what is termed "over-acid". What this means is upon digestion, feed is either acid forming or alkalizing to the system. For example, alfalfa is acid forming, most grass hays are alkalizing, apple cider vinegar is an acid yet upon digestion leaves an alkaline residue, grains are acid forming as well, and fats and minerals are alkalizing. As I have written in the past articles, balance is always the key. The same goes for balancing protein in the horse's diet.
When the diet exceeds 12% total protein, the body has several buffering mechanisms available to offset the deleterious effect of over-acid. Because the heart will not even beat in an over-acid body and the organs must be bathed in an alkaline medium, it is a top priority to keep the body alkaline (apart from the stomach acid). Here is a breakdown of the buffering mechanisms:
1. Because minerals are alkalizing, if minerals are not readily available in the blood stream, the body will pull the minerals from the bones, ligaments, and tendons to buffer the acid.
2. The body will retain water to dilute the acid, thus the horse can be mistaken for being in "good flesh". Once the high protein feed is taken away, the horses will literally urinate themselves thin in a few days to a couple of weeks! They are not losing lean muscle tissue, they are losing the retained water.