Equine gut anatomy and physiology

Question 1

What are the problems of a grazing diet for horses?

Answer 1

Grass contains silicates - harder than enamel => rapid wear of teeth
Cellulose and hemicellulose in diet can’t be digested - required breakdown by bacteria in hindgut

Question 2

Describe horse dentition

Answer 2

Lips and incisors grasp and prehend food
Large, ridged molars grind food
irregular molar surface for optimal grinding
rotational chewing
continued eruption throughout life = rate of wear

Question 3

What is the effect of concentrate diets on horse dentition?

Answer 3

affects chewing movement and rate of wear => overgrowths

Question 4

Why does saliva exit the mouth and nose in horses with choke?

Answer 4

food material stuck in oesophagus => saliva cannot go down oesophagus

Question 5

Why can horses not vomit?

Answer 5

muscular sphincter controlling food moving into the stomach and preventing reflux - blocked stomach => death if no intervention

Question 6

What is choke and what can cuase it?

Answer 6

food obstructing the oesophagus
caused by:
- dry food e.g., sugar beet
- food that is not properly chewed
- unsuitable types of food e.g., whole apples, potatoes, grooming brushes

Question 7

What are the 2 distinct regions of the equine stomach?

Answer 7

squamous epithelium
glandular epithelium

Question 8

what are the sphincters in the equine stomach?

Answer 8

powerful muscular sphincters:
- cardiac sphincter: stops food going back into oesophagus
- pyloric sphincter: controls food entering duodenum

Question 9

Describe the clinical relevance of the equine small intestine

Answer 9

long mesenteric attachment and no fixed position => can form knots

Question 10

Describe the digestion of carbs, protein and fat

Answer 10

Question 11

Why are horses not designed for sugar diets?

Answer 11

fructans cannot be digested in the SI
passed onto LI where they are digested by bacteria => acidic environment => changes large intestinal bacterial flora

Question 12

What are the common disreases of the equine SI?

Answer 12

parasites
diarrhoea
impactions
twists and strangulation
infiltrative bowel disease - malabsorption

Question 13

What is the function of the equine large colon?

Answer 13

microbial digestion of cellulose and absorption of water and electrolytes

Question 14

Where are sacculations and taenial bands found in the equine GIT?

Answer 14

ventral colon
caecum

Question 15

what is the function of sacculations in the equine GIT?

Answer 15

increases SA for microbial fermentation?

Question 16

What is function of taenial bands?

Answer 16

muscular bands important in the mixing and movement of ingesta

Question 17

What is the function and anatomy of the equine small colon?

Answer 17

storage of faeces and absorption of remaining water
Narrow diameter => impactions

Question 18

What structures can be felt via rectal palpation in the horse?

Answer 18

Left hemisphere:
Spleen - against body wall, smooth, sharp border
Caudal pole of left kidney - smooth margins and against spleen
Pelvic flexure - no sacculation or palpable taenial bands, indentable contents, can move to midline
Small colon- small diameter, 2 taenial bands, faecal balls

Right hemisphere:
Caecum - large diameter, gas/fluid/feed contents, sacculations, caudal and medial taenial bands run dorsal to ventral

Question 19

What the possible causes of abdominal disease in horses?

Answer 19

diet
anatomical predisposition
motility disturbances
infection
parasites
ulceration

Question 20

What diagnostic tests should be carried out in suspected abdominal disease in horses?

Answer 20

blood sample - hydration, infection, biochemistry, electrolytes
Nasogastric intubation
Faecal exam
Abdominal paracentesis
Ultrasound

Question 21

What is the function of nasogastric intubation in horses?

Answer 21

Removal of liquid reflux as horses are unable to vomit
detection of gastric impaction
relieving choke
administer oral fluids/treatments

Question 22

What should you analyse in a peritoneal tap of a horse with suspected abdominal disease?

Answer 22

colour
volume
turbidity
total protein
cell number and type