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Protein HOW MUCH SHOULD YOU FEED AND WHEN? Antoinette Foster, Dip Nut Equine Nutritional Therapist and Medical Herbalist.

Of all the different types of feeds in your horse’s diet, protein may be the most misunderstood. Many horse owners are under the incorrect assumption that protein is actually an energy source, however it has a different function, as protein chains of amino acids are the building blocks for growth and repair of bones, muscles, and almost all of the soft tissue in the horse’s body. PROBLEMS WITH OVERFEEDING While it is an extremely important part of the diet, the misconception that more protein is a good thing is not necessarily correct, but it can be equally damaging to have too little protein. Growing horses have a higher requirement for protein than do mature horses TOO MUCH One of the most common issues today is with overfeeding horses in general. Protein is one of the nutrients that is commonly overfed. Protein not used immediately by the horse’s body will be broken down to release nitrogen atoms, those nitrogen atoms become bound up as ammonia and urea molecules. The ammonia and urea are excreted in the urine, this leads to increased water intake, increased urination and you may notice a much stronger ammonia

smell in the horse’s stable. Before excretion the ammonia and urea must be filtered out of the blood, and over time this can have a taxing effect on the kidneys, making them work a lot harder. It is very probable that this can lead to lowered renal function and cause strain on the liver and kidney with the likelihood of liver and kidney disease developing. Excess protein can affect the performance of the horse, and there is some evidence to suggest that too much can interfere with calcium absorption. In one study, weanlings and yearlings fed a diet 25% higher in protein than normal suffered slower rates of growth overall and a higher incidence of developmental bone and joint problems. TOO LITTLE Horses that do not receive sufficient amounts of protein in the diet can suffer in the form of decreased growth and development in young horses, a reduction in appetite, possible body tissue loss, slow hoof growth, a deficiency in energy and poor skin and coat condition. They can have a deterioration of the larger muscle groups of the hindquarters and often will begin eating their manure due to insufficient protein source. Because the protein requirement is a lot less for mature horses than it is for young, growing horses, the risk of complications with insufficient protein is very uncommon. Symptoms may occur with horses that are on very poor pasture or poor-quality hay for a prolonged period. It is very likely that altering the diet can correct the symptoms associated with a protein deficiency. Continued...


Protein ... A lack of protein in the young, growing horse is more likely to be a long-term, genuine issue so when formulating a diet for our horses it is very important to ensure that the protein source is at the required level. WHAT IS PROTEIN? Proteins are chains of amino acids, of which there are 22 that are found in nature. Amino acids contain nitrogen and sometimes sulphur. The horse’s body does not have the ability to produce all the amino acids it needs. Some can be synthesised only by microorganisms or green plants and are called essential amino acids; these can only be sourced by the horse from the environment. The non-essential amino acids are synthesised by the horse

The horse’s body does not have the ability to produce all the amino acids it needs. Some can be synthesised only by microorganisms or green plants and are called essential amino acids; these can only be sourced by the horse from the environment.

When protein is consumed by a horse the amino acids are broken down in the digestive tract by enzymes and acids. The individual amino acids are absorbed via the wall of the small intestine where they remain somewhat unchanged from the original chemical composition. Some find their way into the bloodstream via the liver, which has the ability to alter some amino acids into different forms as needed. They then move to various locations around the horse’s body where they are needed most for growth and repair of tissues.

IT IS IMPORTANT TO PROVIDE A HIGH-QUALITY SOURCE OF PROTEIN SO THERE ARE SUFFICIENT ESSENTIAL AMINO ACIDS SUPPLIED. Lysine is an extremely important amino acid and is often referred to as the first limiting amino acid, which means that if insufficient quantities are supplied the horse’s body will find it difficult to utilise other amino acids that are available. A few of the functions amino acids are responsible for include an involvement in the composite and release of hormones, of neurotransmitters and enzymes and they regulate sleep, appetite and blood pressure. Possibly the most important aspect of amino acids is to assist with the repair of muscle tissue and other soft tissues throughout the body as they account for approximately 80% of the horse’s total structure.

When protein is consumed by a horse the amino acids are broken down in the digestive tract by enzymes and acids.

PROTEIN BUMPS We have all heard the word ‘protein bumps’, which are small, round, elevated bumps on the skin. Horses can develop these bumps for no apparent reason, but they can be itchy and cause irritation to the horse. While insect bites and other various reactions to pollutants, chemicals and pollen, or even parasites, can also cause a reaction in the form of a raised bump on the skin surface, protein bumps appear to be an allergy to a specific protein. To alleviate this problem it is necessary to determine which source of protein is causing the irritation and then remove this from the diet. Many by-products, some of which are not suitable for horses, can cause irritation and sometimes this can be due to the protein source being unsuitable for the horse’s digestive system. The amino acid profile of a specific feed is of higher importance when feeding a young, growing horse than feeding a mature horse as the mature horses tend to be less sensitive to diverse types of protein quality. PROTEIN AS ENERGY It is highly impractical to use feeds that are high in protein as an energy source for your horse. Although protein can be an energy source it is not recommended, as it would be quite an expensive way to provide the animal with the correct energy level. Protein provides a much lower level of energy in comparison to carbohydrates and fats, and when fed in higher levels provide a higher heating factor, which can cause excessive sweating, particularly in hot weather. HOW MUCH IS IN THE FEED? As the horse feed industry is not regulated, it is very easy to use different types of by-products and ingredients to have the protein level look extremely good on the labelling of the bag of feed. However, crude protein numbers do not reflect protein quality. Crude protein is based on the overall nitrogen content of the feed. Not all the nitrogen in feed is necessarily protein-bound and may therefore not be as efficient. Protein can be found in all forms of horse feed, including pasture, hays - whether they are legume or not - grains and the many sweet feeds and pellets available on the horse feed market today.


A mature horse (average weight of 500kg) needs about 0.64kgs of protein a day for maintenance, early pregnancy, or light work. The horse usually ingests at least this much protein by grazing or eating grass hay (dry matter intake of about 10kg). A mature horse doing moderate to heavy work needs about .975kgs of protein a day. An owner could feed 10kg of grass or hay and add 907g-1.8kg of fortified feed to meet the protein requirement. Reliable sources of protein can be found in many feeds, but always look for a quality form, this means a feed that does not contain byproducts, but one that contains a range of natural ingredients such as alfalfa hay, oaten hay and grains (oats, barley). A good natural daily formula would be of benefit with working horses. HOW MUCH PROTEIN SHOULD I FEED? To be precise about the level of protein for each individual horse is difficult, as guidelines change all the time. As there are many different forms of protein it can be a bit confusing when one reads the label on a bag of feed. Like any part of the horse’s diet the required amount of protein will depend on the individual horse, particularly if it is a horse that is still growing. We know that when we are formulating a diet for horse that we must take into consideration many factors. The digestibility of the type of protein and the size of the horse’s feed will also have an impact. A value of 0.60g of digestible protein per kilogram of body weight per day is appropriate for most adult horses.

Broodmares in the last trimester, which is when the foetus undergoes approximate 60% of its development, will require an increase in protein levels. Lactation also demands a higher protein intake. As an example, horses in hard work - such as a three-day eventing horse - do require a high level of protein in the diet to support the increased muscle development and mass but also to replace nitrogen lost in sweat. However, this increase is quite small, only 1% to 2%.

RECOMMENDED PROTEIN LEVELS FOR HORSES Classification Nursing foal, 2-4 months (needs above milk)

Protein Level 16

Weanling at 4 months

14.5

Weanling at 6 months

14.5

Yearling (12 months)

12.5

Long yearling (18 months)

12

2-year-old (24 months)

11

Mature horse maintenance (idle)

8

Mature horse in light work (e.g. pleasure riding)

10

Mature horse in moderate work (e.g. jumping, cutting, ranch work)

10.5

Mature horse in intense work (e.g. polo, racing, endurance)

11.5

Stallion in breeding season

10

Pregnant mare–first nine months

8

Pregnant mare–9th and 10th months

10

Pregnant mare–11th month

11

Nursing mare–first three months 13

13

Nursing mare–from third month on

11

Taken from Lon D. Lewis’ Feeding and Care of the Horse, 2nd edition (1996) one of my favourite books on feeding horses.

WHICH FEEDS PROVIDE THE BEST PROTEIN? Animal sources, such as milk and egg protein, fish and meat protein have the best amino acid profile and the highest levels of lysine, however horses are strict herbivores so all of the above are simply not suitable to feed to any horse. The best plant sources are oral-grade soy products in the form of flour or meal and even canola. These are exceptional plant protein forms as they contain an adequate amount of lysine and methionine. Grains such as oats, corn and barley contain approximately 8 to 20% protein, but the quality is not high. Legumes, such as alfalfa (lucerne), have a really good level of protein and are an excellent source of other valuable nutrients, such as calcium and some vitamins. Learning to understand and read a feed label can be very beneficial; look for products that are as natural as possible. This includes feeds that contain no by-products, molasses and other ingredients not suitable for your horse. As all types of feed contain protein it is a matter of determining your horse’s individual needs and then calculating what may be best suited. While protein is an extremely important part of your horse’s diet it must be put into perspective as it is only one part of a complete balanced feed that is required to maintain healthy horses.

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PROTEIN - how much to feed and when to feed it.  

Many horse owners are under the incorrect assumption that protein is actually an energy source, however it has a different function, as prot...

PROTEIN - how much to feed and when to feed it.  

Many horse owners are under the incorrect assumption that protein is actually an energy source, however it has a different function, as prot...

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