Protein in a horse’s diet
Protein in a horse’s diet
After water, protein is the most common substance in the horse’s body, from the brain to the hooves. Protein is not only muscle mass. These are enzymes, antibodies, DNA / RNA, hemoglobin, cellular receptors, cytokines, most hormones, connective tissue. Needless to say, protein (aka protein) is a very important component of the diet.
The structure of a protein molecule is so complex that it is amazing how it is digested at all. Each colored ball in the picture is a chain of amino acids. The chains are connected to each other by certain chemical bonds, which form the sequence and shape of the resulting molecule. Each protein has its own set of amino acids and its own unique sequence of these amino acids and the form into which they are ultimately twisted.
Protein molecules undergo primary “processing” already in the stomach – under the influence of gastric juice, the molecule unwinds, and some bonds between the chains of amino acids break down (so-called “denaturation” occurs). Further, in the small intestine, the resulting chains of amino acids under the influence of the protease enzyme coming from the pancreas break down into individual amino acids, the molecules of which are already small enough to pass through the intestinal wall and enter the bloodstream. Once in the body, amino acids are collected back into the proteins needed by the horse.
I’ll make a small digression: recently there have been some feed manufacturers who claim that the protein in their feed is not processed in any way and therefore is not denatured and retains its biological activity, in contrast to competitor feeds in which proteins are denatured and lose their biological activity in the process heat or other processing. Such statements are nothing more than a marketing ploy! Firstly, getting into the gastrointestinal tract, any protein is immediately denatured, otherwise a huge protein molecule simply cannot be absorbed into the blood through the intestinal walls. If the protein is already denatured, it will simply be digested faster, because you can skip the first step. As for biological activity, it means functions that a specific protein performs in the body. In relation to a horse, the biological activity of plant proteins (for example, photosynthesis) is not really needed for it. The body itself collects proteins from individual amino acids with the biological activity necessary for this particular organism.
Proteins that do not have time to digest in the small intestine enter the posterior part of the intestine and there, although they can nourish the local microflora, for the horse organism are already quite useless (from there they can only proceed). A side effect can be diarrhea.
The body is constantly breaking down existing and the synthesis of new proteins. In the process, some amino acids are produced from other existing ones, some that are currently unnecessary, are eliminated from the body, because the horse’s (and any other, probably) organism’s ability to store protein for the future does not exist.
Moreover, the amino acid is not excreted in its entirety. An amino group containing nitrogen is separated from it, and it is excreted after going through a difficult transformation path in the form of urea with urine. The remaining carboxyl group is stored and can be used to generate energy, although this method of generating energy is rather complicated and energy-consuming.
The same thing happens with excess amino acids that have been ingested as part of protein with food. If they have time to digest and absorb into the blood, but the body does not need them at the moment, nitrogen is separated and excreted in the urine, and the remaining carbon part goes into reserves, usually fat. The stall smells stronger of ammonia, and the horse increases water consumption (urine must be produced from something!)
The above leads us to the question of not only the quantity, but also the quality of the protein. An ideal protein quality is where all the amino acids are in exactly the same ratio as the body needs them.
There are two problems. First: while it is not known exactly what kind of quantity it is, the more it will change depending on the state of the body. Therefore, at the moment, the ideal is the ratio of amino acids in horse muscles (and in lactating mares – also in milk), since muscles are still the bulk of the protein. To date, the total need for lysine has been more or less accurately studied, so it is normalized. In addition, lysine is considered the main limiting amino acid. This means that very often feeds contain less lysine than necessary compared to other amino acids. That is, even if the total amount of protein corresponds to the norm, the body will be able to use it only as long as it has enough lysine. Once lysine is over, the remaining amino acids cannot be used and will go out.