Equine Digestive System Anatomy and Function

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Equine Digestive System Anatomy and Function

• Paul D. Siciliano, Ph.D.
• Associate Professor Equine Nutrition
• Dept. of Animal Science
• Equine Science Program

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Overview

• Nutrients
• Basic digestive system anatomy
• Process of digestion

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Nutrients

• Defined
• Any chemical element or compound in the diet
  that supports normal reproduction, growth,
  lactation or maintenance of life processes

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Nutrients

• Classified
• Water
• Carbohydrates
• Protein
• Lipids
• Minerals
• Vitamins

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Nutrients

• Functions
• Structural Components
• Ex Protein is a structural component of muscle
• Catalytic
• Ex Enzymes are proteins
• Regulatory function
• Ex Vit. D, in active form, is a hormone
• Energy
• Ex Some CHO are oxidized to produce ATP.

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Nutrients

• Distribution in feeds

Carbohydrates 70 to 80 DM
Proteins 5 to 20 DM
Water 8 to 80
Lipids 2 to 3 DM
Vitamins 1 to 2 DM
Minerals 2 to 4 DM
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Nutrients

• Distribution in feeds

Carbohydrates
Carbohydrates -Structural (cell wall)
Carbohydrates -Non-structural (non-cell wall)
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Overview

• Nutrients
• Basic digestive system anatomy
• Process of digestion

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Basic Digestive System Anatomy
2-4 gal
50-70 ft
3-4 ft 7-8 gal
10 ft 5 gal
10-12 ft 14-16 gal
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Overview

• Nutrients
• Basic digestive system anatomy
• Process of digestion

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Digestion defined

• Preparation of food for absorption

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Digestion

• Types of digestion
• Mechanical digestion
• Chemical
• Endogenous
• Microbial

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Absorption

• Passage of digested nutrients from lumen of the
  gut across the mucosa and into the bloodstream or
  lymph for transport to tissues

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Mouth Functions -prehension -mastication
-swallowing
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Mouth

• Prehension
• lips/incisors
• allows for selectivity of feeds

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Mouth

• Mastication
• increased surface area for digestive action of
  enzymes

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Mouth

• Swallowing
• tongue serves as a plunger

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Mouth

• Saliva
• lubricant
• limited digestive action
• buffer pH in the stomach

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Mouth Functions -prehension -mastication
-swallowing
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Esophagus

• Conduit from the mouth to the stomach
• No digestive secretions
• No reverse peristalsis
• Cant regurgitate feed

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Stomach

• Digestion
• initiation of protein digestion
• Some microbial fermentation

Non-glandular region
Glandular region
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Stomach

• Residence time is relatively short
• Two to six hours (slightly longer in foals)
• 98 empty by 12 hr post meal
• Implications on
• Digestion
• Health

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Small Intestine

• Primary site of digestion and absorption for
• Starch and simple sugars
• Triglycerides and fatty acids
• Proteins and amino acids
• Several minerals and vitamins
• Digestion occurs primarily by
• Endogenous enzymes
• Pancreas
• Intestinal mucosa
• Some microbial digestion occurs
• Relatively small amount

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Small Intestine Fluid balance
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Small Intestine

• Rate of Passage
• Relatively fast
• Estimates of 1 ft/min
• 70 to 100 ft in length

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Cecum and Large Colon

• hindgut
• No secretion of digestive enzymes
• Microbial fermentation

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Microbial Fermentation
Microbe
Fibrous Non-Fibrous Carbohydrate
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Small Colon

• water absorption
• Formation of fecal balls

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Summary of Major Sites of Nutrient Digestion and
Absorption
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Time of Ingesta Passage Through the Total Tract
and Various Segments of the G.I. Tract
Total Tract
Stomach
Small Intestine
Hind-Gut
Hours
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Overview

• Nutrients
• Basic digestive system anatomy
• Process of digestion
• Practical application?

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Forage should be the foundation of equine rations
Periodic Grazers
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Forage should be the foundation of equine rations
Periodic Grazers
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Questions???