The Digestive System

Basic Information  Converts feed into a form that can be used by the body for maintenance, growth and reproduction  Mature light horse: 100 feet long, gallons  Stomach makes up less than 10% of total capacity of the digestive track

Mouth  Lips pick up feed and is passed to the mouth by the action of the tongue  Grazing food is grasped by incisor teeth  Food is masticated between molar and cheek and mixed with saliva  Saliva moistens and lubricates the food for swallowing  Food is forced past the soft palate into the pharynx by the base of the tongue

Pharynx  Short, somewhat funnel-shaped, muscular tube between mouth and esophagus  Muscular action forces food into the esophagus  Food or water cannot return to the mouth  Due to the traplike action of the soft palate a horse cannot breathe through their mouth

Esophagus  Muscular tube extending from the pharynx down the left side of the neck and through the thoracic cavity and diaphragm to the stomach  Food forced down by a progressive wave of constriction of the circular muscles of the organ  Food or water through nostrils is almost certain indication that the horse has choked because esophagus has been blocked  Esophagus enters the stomach through an oblique angle, making regurgitation impossible

Stomach  U-shaped, muscular sac in the front part of the abdominal cavity  Food entering is arranged in layers  End next to small intestine fills up first  Contents of the stomach are squeezed and pressed by the muscular activity of the organ  Digestive juice secreted by walls of stomach is known as gastric juice

Small Intestine  Stomach to cecum  Tube that is about 2in in diameter and 70 feet long  Holds about 12 gallons  3 parts  Duodenum  Jejunum  Ileum  Lies in folds and coils near left flank

Large Intestine  Divided into cecum, large colon, small colon, rectum, and anus  Consume large quantities of cellulose in diet  Usual digestive enzymes are not effective against cellulose so horse must rely upon bacteria to break down cellulose into substances it can be absorbed into body  To give bacteria time to act on cellulose, the cecum and the large colon in the horse have been greatly enlarged

Large Intestine  Cecum is elongated sac  Contents are always liquid  About 4 feet long, 8 gallon capacity  Large Colon  Extends from cecum to small colon  12 feet long, 20 gallon capacity  Bacterial action and some digestion of food takes place

Large Intestine  Small Colon  10 feet long  Extends from large colon to rectum  Contents usually solid; here the balls of dung are formed  Moisture in food is reabsorbed here  Rectum  12 inches long  Extends from small colon to anus  Where digestive tract ends

Needs for Feed  Major sources of energy and protein are grain and roughages  Feeding is both an art and a science  Require nutrients to maintain body weight and support digestive and metabolic functions  Need additional nutrients for growth, work, reproduction and lactation  Most receive their daily ration in two parts: roughages and concentrates

Balanced Rations  Balancing rations should:  Furnish horses with a daily supply of nutrition in the correct amounts  Supply palatable, easily obtained feedstuffs  Provide feedstuffs economical for the conditions

Feeds  Four groups  Roughages  Concentrates  Protein Supplements  Minerals

Example Ration IngredientsPounds to Make ½ TonPounds to Make 1 Ton Oats (crimped or crushed) Corn (coarsely cracked) Soybean Meal (44%) Molasses (liquid)70140 Dicalcium phosphate1530 Limestone1020 Salt (trace mineral)510 Vitamins A, D, E to supply 4000 IU/lb -- Total Pounds Foal Creep Ration: should not be used after weaning because it is too high in protein and calcium unless fed with a nonlegume hay

Calculating Nutrients  Follow these steps: 1. Know what the horse requires 2. Know what kind of feed will fill those requirements economically 3. Know what feeds are palatable 4. Know how much of a given feed the horse can eat 5. Know how to calculate the amount of a nutrient in a feed

Example  What is the protein content of a feed that contains 500lbs of oats, 400lbs of corn and 30lbs of soybean meal 1. Find the protein content of each of the feedstuffs 2. Multiply this value by the number of pounds of the feedstuff into the mixture 3. Next find the total pounds of protein in the feed mixture 4. Finally, divide the total amount protein in the feed mixture by the total weight of the feed mixture and convert to a percentage

FeedstuffProteinPounds in MixProtein in Mix Oats0.118lb/lbx500=59lbs Corn0.091lb/lbx400=36lbs Soybean Meal0.445lb/lbx30=13lbs Total930108lbs 108lbs of protein in mixx 100=11.6percent protein 930lbs of feed mix