Protein in Horse Feed: Protein Requirements Horses Need and Why Protein Quality Matters
When you read the feed label and it says 10 or 12 % protein, this is just a measure of the amount of protein present. The information is a little misleading. The amount is calculated from measuring the amount of nitrogen present in a sample, and taking that 16% of protein is
nitrogen, and doing a back calculation. This tends to overestimate the amount of actual protein present since there is some nitrogen in the feed that is not in a protein. It also tells you nothing about the quality of the proteins in the feed.
How Much Protein Do Horses Need?
Protein is a vital nutrient in a horse's diet, but the quantity needed varies depending on the horse's age, workload, and physiological condition. When considering protein requirements, it's important to focus not just on the total amount of protein but also on the quality of that protein. High-quality proteins provide essential amino acids, the building blocks of proteins, in the correct proportions that horses need for optimal health.
Crude protein is a term often used in horse feeds, which refers to the total protein content without regard to the protein's quality or digestibility. While the crude protein level gives an indication of the total protein present in the feed, it's the amino acid profile that determines the protein's quality. Lysine, methionine, and threonine are the limiting amino acids in equine diets, meaning they are the most likely to be deficient and thus limit protein synthesis.
Adult, idle horses typically need about 8-10% of their diet as crude protein, while growing foals and lactating mares require higher amounts, around 16-18%. This protein requirement increases with workload, as horses use protein for energy during exercise. It's crucial for horse owners to remember that too much protein can lead to health issues such as kidney damage and excessive thirst. Therefore, it's essential to balance the protein ration to match the horse's needs without exceeding them.
Common Sources of Protein in Horse Feed
Forages, including grass and legume pastures, are the primary source of protein for most horses. Legumes like alfalfa and clover usually have higher protein content than grasses. For example, alfalfa typically contains 15-20% crude protein, making it a high-quality source of protein.
Supplemental feeds like soybean meal also provide a high protein content with a good balance of essential amino acids, making it a common choice for horse feeds. Soybean meal usually has a crude protein level of 44-48%, with a high lysine content, an essential amino acid that serves as a building block for protein.
Horse feeds also commonly include grains and processed feeds, though these tend to be lower in protein and higher in starch. When considering the protein quality in these feeds, it's essential to look at the amino acid profile. High-quality proteins will provide all the necessary essential amino acids in the correct proportions.
In conclusion, understanding the protein quality and the sources of protein in horse feeds is important for meeting the protein requirements of horses and ensuring their optimal health. For horse owners, a balanced diet that provides adequate amounts of high-quality protein is essential. With the right nutrient balance, you can ensure that your horse is getting the protein it needs.
What are Amino Acids?
Amino-acids are complex molecules that are the primary components of protein chains. There are 22 amino acids that compose all the proteins the body makes and uses. 12 of these can by synthesized in the liver, the other 10 must be supplied in the diet, these are the 10 essential amino acids. The non-essential amino acids are Alanine, Asparagine, Aspartate, Glutamate, Glutamine, Glycine, Hydroxyproline, Hydroxylysine, Proline, Serine, Tyrosine. Cysteine can be regarded as a non-essential amino acid since it can be synthesized from Methionine, but only if sufficient
methionine is supplied. The essential amino acids are Arginine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. These amino acids must be present in the feed and be picked from the GI tract.
There is no body store of amino acids, they exist as pool within the liver and within each cell, thus if one of the essential amino acids is missing or in too low a quantity, protein synthesis stops at the point where that amino acid is needed and cannot continue until it is obtained. All the other amino acids tend to accumulate and can be a problem, so they tend to be transported to the liver, and metabolized into urea. The urea is transported to the kidneys where it is excreted in the urine. Since it is the amount of the essential amino-acids which limit the synthesis of protein, feeding a low quality protein in high amounts, means there are a lot of unusable amino-acids around, this tends to result in a high output of urine with a strong smell of ammonia. Most plant proteins are lower in essential amino acids than animal proteins, however horses being herbivores can only eat limited amounts of animal protein, the only safe one to use is whey protein which derived from milk.
Horses can utilize whey since they have drunk milk as foals. Another way is to use vat grown amino acids produced by bacteria.in a pure crystalline form. Supplying the essential amino acids, means that the horse can continue to synthesize the proteins needed. It also means that there a fewer of the non essential amino-acids to be dumped, and the urine output is decreased. Protein is an essential nutrient, but it needs to be of sufficiently high quality if it is to be used efficiently.
What does the amino-acid profile mean?
Proteins are chains of amino-acid molecules, like letters in a word the sequence of the amino- acids makes the protein a specific shape and controls its function. When the cell manufactures a protein, say an enzyme needed, the ribosomes (a small organelle within the cell) gets instructions from the nucleus, it adds the requires amino-acids one at a time to the chain. The protein chain twists and turns and develops its characteristic shape. If the amino-acid needed is not present in the cell, the process stops, until the required amino-acid is found. Thus, a shortage of individual amino-acids usually presents its self as a general slowing down of protein synthesis.
What is Protein Quality?
Protein quality is a measure of how closely the amino-acid profile of the protein matches the amino-acid requirements of the horse. The main difference in protein quality is how much of the essential amino-acids the feedstuff supplies. Crude protein content, as stated on feed tags, gives a measure of the total protein in the feed, but it doesn't distinguish between different amino acids or assess their digestibility. However, it's the digestible essential amino acids that determine protein quality.
A high-quality protein source contains all the essential amino acids a horse needs, in proportions close to those required for protein synthesis in the horse's body. For example, lysine is the first limiting amino acid, meaning it's the one most likely to be in shortest supply relative to the horse's needs. If a protein source is low in lysine, it's considered a low-quality protein, regardless of its total protein content.
Protein quality matters because if a horse consumes a diet low in one or more essential amino acids, it can limit protein synthesis, even if the total protein intake meets the horse's crude protein requirement. This situation can lead to protein deficiency, which can affect growth in young horses, lactation in mares, and muscle protein maintenance in performance horses.
How to Increase Quality Protein for Your Equine
To ensure the protein quality in a horse's diet, horse owners should choose feeds containing high-quality protein sources. These include alfalfa, soybean meal, and certain commercial feeds, which are often fortified with essential amino acids. It's also crucial to consider the digestibility of the protein, as not all the protein a horse consumes from a particular feed is absorbed and used by the body.
For example, cereal grains may have a high percent crude protein on a dry matter basis, but they are often low in lysine, a key essential amino acid. On the other hand, hays, particularly legume hays like alfalfa, contain high-quality protein with a good balance of essential amino acids.
Protein needs change based on the horse's life stage and work level. For instance, young growing horses and lactating mares require higher protein levels compared to a mature horse in light work. Therefore, adjusting the protein sources and levels according to these needs is important.
Feed manufacturers often supplement feeds with specific amino acids to increase protein quality. This strategy is especially beneficial when the diet's primary components, such as grass hays, are lower in quality protein.
In summary, increasing the quality of protein in a horse's diet involves a combination of selecting high-quality protein sources, considering the balance of essential amino acids, and adjusting protein intake according to the horse's individual needs. By doing so, many horse owners can ensure their horses are getting the right protein to support their health and performance.