RED DEER – A horse’s digestive system is like a fine machine: there could be trouble if the wrong fuel is added.
The horse has evolved as a grazing animal with a unique digestive system, says equine specialist Bob Coleman of the University of Kentucky.
“It was well designed for a forage-consuming trickle feeder,” he told the Alberta Horse Breeders and Owners conference held in Red Deer Jan. 17.
“This animal was born to eat grass with continual forage intake over 12 to 14 hours.”
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However, modern horse owners must often schedule meals because of other commitments, and horses have adapted.
A horse can digest more efficiently if it grazes slowly all day. It eats about two percent of its body weight throughout the day, and gut health and nutrient absorption are better if the feed passes through slowly.
“If we overwhelm the system, it takes time. We need to make sure the flow through in the system gives them time to break it down,” Coleman said.
“Depending on what we feed, it will affect the role each section of the tract plays.”
Understanding gut function makes it easier for horse owners to understand why serious upsets may occur.
The digestive system processes the feed and absorbs nutrients. It consists of a fore gut and hind gut. These are unique environments and are capable of extracting nutrients from a wide variety of feed.
Feed intake starts at the mouth. Horses produce saliva when they chew, which releases enzymes and bicarbonate. This is not digestion. Instead, saliva moistens the feed and the bicarbonate provides a buffer against stomach acid.
The horse’s esophagus is 120 to 150 centimetres long and leads to the stomach, which contains gastric juices and acid.
Digestion time in the stomach is short, and food moves to the small intestine, a 18 to 21 metre long organ that is only five cm in diameter. It secretes enzymes for digestion of protein, sugar, starch and fat.
Digested material takes 90 minutes to pass through to the hind gut, where microbes break down fibre. Water absorption happens here.
The cecum is in this area. It is 90 to 120 cm long and has up to 300 litres of capacity.
The large colon is the next stage and harbours a large microbial population. This is where impacting may occur, especially if horses receive low quality hay and eat snow. They don’t receive enough water and cannot produce enough saliva.
It may take up to 40 hours for final digestion to happen in this area.
The small colon is three metres long and is the final site of water and mineral absorption.
