THE EQUINE DIGESTIVE SYSTEM Types of Digestive Systems

THE EQUINE DIGESTIVE SYSTEM

Types of Digestive Systems n Monogastric q q n Ruminants q q n simple-stomach humans, pigs, dog, monkey multiple stomachs cattle, sheep, goat Pseudo-Ruminants (Functional Cecum) q horse, rabbit, hamster, guinea pig

IT’S A HORSE, OF COURSE n Not a ruminant! q q n Modified non-ruminant Hind-gut fermentator More efficient than non-ruminants in digesting cellulose and hemi-cellulose. q Cellulose and hemi-cellulose are found in large quantities in roughages such as grass and hay.

HORSE DIGESTIVE SYSTEM

IT’S A HORSE, OF COURSE n MOUTH q q q Use their teeth to grab and rip the grass from the roots. Jaw movement is both vertical and lateral…tear grass fibers between their jaws. Upper jaw is wider than the lower jaw, so mastication only occurs on one side of the mouth at a time n This is why the horse develops sharp points on the inside and outside molars that require ‘floating’.

IT’S A HORSE, OF COURSE n ESOPHAGUS q One-way peristalic action! n n q q Cannot regurgitate Do not ‘chew their cud’ Horses cannot ‘burp’ or pass gas through their esophagus. Because they do not ‘chew their cud’ (or re-chew their food) the grass and hay fragments tend to be longer. n Poor quality, tough or stemmy hay is difficult for the horse to tear apart and chew.

IT’S A HORSE, OF COURSE n STOMACH q q Smallest stomach of all farm animals, in proportion to the animals body size. Lacks extensive muscular movement n n q Food tends to layer, not mix Does not contribute to the mechanical breakdown of food Stomach secretes n n HCL Enzymes

IT’S A HORSE, OF COURSE n SMALL INTESTINE q Horse does not have a gallbladder, so there is no storage of bile from the liver. n q Bile is critical to the digestion of fats. In most animals it is stored so that large quantities of fats can be consumed and digested. Bile is secreted directly from the liver into the duodenum, or the first part of the small intestine. n Makes it necessary for horse to consume small meals several times a day

IT’S A HORSE, OF COURSE n LARGE INTESTINE q q Accounts for 60% of the total volume of the gastro -intestinal tract. Divided into four parts n n Cecum Large Colon Small Colon Rectum

IT’S A HORSE, OF COURSE n LARGE INTESTINE q Cecum and Large Colon n n Contain active bacteria similar to the microbes of the rumen Bacterial breakdown of cellulose and other carbohydrates results in Volitale Fatty Acids (VFA’s) q n VFA’s are used as a source of energy by the horse, similar to glucose or other sugars. The bacteria also make: q q All of the water-soluable vitamins Some proteins

IT’S A HORSE, OF COURSE n LARGE INTESTINE q Small Colon n Primary area of water absorption

What does the design of the Equine Digestive System tell us? n Only one chewing! q n Cannot burp or regurgitate! q n Require good quality hay so that it can be ‘destroyed’ into small digestible pieces the first time! When the have an upset stomach or too much gas it can only go one direction…. and it has a long way to go! Small Stomach q q Designed for several small feedings during the day. Not very active, food tends to layer. n Without adequate moisture…WATER, the food will not move through to the small intestine and it will ferment. q Fermentation = gas.

What does the design of the Equine Digestive System tell us? n No Gall bladder q n Majority of the digestion of fats, proteins and carbohydrates occur in the small intestine q n Not prepared for a large meal…again, designed for several small meals during the day. The small intestine is before the large intestine! The grass and hay that is consumed is not digested until it reaches the large intestine! q High quality hay/grass will be more readily digested in the large intestine and offer more nutrients for absorption in the small intestine.