Equine Digestion: From Mouth to Manure

Date: May 8th, 2018

Mouth

Mastication (chewing) is the first stage of digestion where feed is ground down to allow enzymes and bacteria to attack the cell wall of the horse’s plant based diet. It is the only time saliva is produced in horses and it is the physical action of chewing that activates the 3 pairs of salivary glands. Saliva acts as a buffer to prevent choke and 10-12L are produced daily in horses fed a largely fiber diet.

The bicarbonate produced by the salivary glands protects the stomach from acid damage and contains small amounts of amylase which starts the breakdown of carbohydrates. The more chewing, the more saliva that is produced. Concentrate feeds require 800-1200 chews per kg whereas forage requires 3000-3500 chews per kg.

Dental issues can affect mastication, which in turn affects the rest of the digestive process. Regular dental checkups should be a routine part of horse care.

A cutout of a horse's digestive system

Foregut: stomach and small intestine

The equine stomach is quite small relative to the size of the horse. It is divided into two sections: glandular and non-glandular. The non-glandular region is the first area to encounter food. It depends on mucous and buffers from saliva to protect it. This is the region where 80% of ulcers are found! The glandular region continuously produces hydrochloric acid which further breaks down food.

Pepsinogen and stomach acids initiate the digestion and degradation of fats and proteins. The stomach regulates the passage of food as well as mixes it via muscular contractions known as peristalsis.

Small Intestine: The majority of proteins, soluble carbohydrates and fats are broken down by digestive enzymes here. The pancreas releases amylase into the small intestine for carbohydrate breakdown. Proteases continue the breakdown of proteins into amino acids. Bile from the liver help emulsify fats into smaller globules. The nutrients are then absorbed into the bloodstream through the intestinal villi. Healthy villi allow for maximum absorption of nutrients. Damage can lead to leaky gut; as the cells are damaged the membrane barrier is compromised, allowing toxins and large molecules into the bloodstream. This can result in body inflammation and suppressed immunity. It can also cause laminitis, founder, colic, GI tract inflammation and malabsorption of nutrients among other metabolic issues. Damage to the small intestine can also be the result of medications, ulcers and parasite overload.

Hindgut: cecum and colon

Small Intestine: The majority of proteins, soluble carbohydrates and fats are broken down by digestive enzymes here. The pancreas releases amylase into the small intestine for carbohydrate breakdown. Proteases continue the breakdown of proteins into amino acids. Bile from the liver help emulsify fats into smaller globules. The nutrients are then absorbed into the bloodstream through the intestinal villi. Healthy villi allow for maximum absorption of nutrients. Damage can lead to leaky gut; as the cells are damaged the membrane barrier is compromised, allowing toxins and large molecules into the bloodstream. This can result in body inflammation and suppressed immunity. It can also cause laminitis, founder, colic, GI tract inflammation and malabsorption of nutrients among other metabolic issues. Damage to the small intestine can also be the result of medications, ulcers and parasite overload.

The PH and balance of microorganisms in the cecum is critical to proper hind gut function. Situations that lower PH, creating an acidic environment or cause death of some of these microorganisms, can cause an imbalance of essential components of the micro-biome. This can result in the release of endotoxins into the blood stream potentially causing an array of issues including laminitis, founder, colic and leaky gut. Continual exposure to low PH can cause anorexia or malnutrition, colitis (inflammation of the colon) and other metabolic disorders.

An increase in the volume of undigested starch and fructans in the hind gut creates an overabundance of starch digesting bacteria which release lactic acid. Normally, horses also have lactate utilizing bacteria which are there to protect from this bacterial flourishing by converting lactic acid to volatile fatty acids thereby keeping the hindgut PH at a neutral level. However, studies have shown that the bacterial populations from one horse to the next can react differently to the same situations. One recent study demonstrated a significant difference between the microbiomes of healthy vs metabolic horses.

Other factors contributing to PH and micro-biome imbalance can be sudden diet changes, intolerance to certain hays and processed feeds, ulcers, stress, dental issues and extended periods between meals. Physical signs may include a swollen cecum (right side in front of the hip) difficulty bending to right under saddle, gut agitation and loose manure.

Large intestine: This section makes up more than half the total volume of the digestive tract. As the fermented food passes through the large intestine, it is exposed to intestinal mucosa for resorption of water, electrolytes and volatile fatty acids. Fibre in the large intestine creates a constant water reservoir to prevent dehydration.

If the cecum has an acidic environment, this can spill over into the large intestine causing damage, which can lead to diarrhea, dehydration, poor absorption of nutrients, colic, ulcers and colitis.

Rectum & Anus

If the cecum has an acidic environment, this can spill over into the large intestine causing damage, which can lead to diarrhea, dehydration, poor absorption of nutrients, colic, ulcers and colitis.

Conclusion

Each horse is an individual. What works for one may not work for another. This is evidenced by the fact that even hay tolerance, the main staple of the equine diet, may vary from horse to horse. Sugar levels, fibre levels and even particular types of grasses will affect each horse differently. This is especially important if they already have digestive issues or are compromised in some way. Unfortunately, at this time, gastric endoscopy performed by qualified veterinarians is only reliable as an imaging tool in the stomach and proximal segment of the small intestine. The type of damage and/or degree of damage throughout the remainder of the GI tract is usually speculative and based on other symptoms that the horse is exhibiting. Unexpected symptoms of GI issues include allergies, skin sensitivity, hives, poor coat, hoof and body condition, poor performance, irritability, and wood chewing to name a few!

What can you do to ensure a healthy digestive tract?

Providing your horse with a feed program as close to nature as possible including access to quality hay or forage at all times or at the minimum, at least 4 meals per day and access to fresh water at all times is the best start. Include regular exercise and regular health checks. Within your ability, avoid preservative and GMO containing feeds.

Add G’s Formula to your daily routine. Why? To provide nature’s best sources of digestive healing aids.

Research testing of a diet rich in beta glucans and glutamine in mice has shown to improve the immune response and improve gut health in compromised animals due to a reduction in inflammation and improvement in intestinal tropism.

G’s Organic Solutions is currently funding similar studies in horses at a recognized university research centre.

We are often asked "why do some horses show improvement in 48 hours and some take 4 months when given G's Formula for horses"? Although most cells in the horse GI tract are replaced every 2-6 days, ulcer damage, ongoing diet issues, or a myriad of other reasons, can lead to deeper and more chronic issues which translates into variable healing times. If you are planning on putting your equine companion on G's Formula, be patient and be consistent. True healing takes time.

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