Horses

Question 1

Describe the structure of the equine large intestine.

Answer 1

Consists of the cecum, large colon, small colon, and rectum.

Question 2

Describe the structure of the large colon.

Answer 2

Divided into the right ventral colon, left ventral colon, left dorsal colon, and right dorsal colon, forming a double U-shaped loop.

Question 3

What are sacculations in the equine large intestine?

Answer 3

• Pouch-like structures in the colon.
• Formed by longitudinal bands of smooth muscle (teniae) that contract and gather the intestinal wall.

Question 4

What is the function of sacculations?

Answer 4

1. increase surface area for microbial fermentation.
2. Mix digesta thoroughly, exposing it to microbes.
3. Prolong digesta retention time for more complete breakdown of fiber and absorption of volatile fatty acids (VFAs).

Question 5

What is the pelvic flexure, and why is it significant?

Answer 5

A sharp, narrow bend where the left ventral colon transitions into the left dorsal colon.

Question 6

What is the role of the cecum in the equine digestive system?

Answer 6

• A fermentation vat where microbial digestion of fibrous material occurs.
• Contains a diverse microbial population that breaks down cellulose into volatile fatty acids (VFAs).

Question 7

How does the small colon differ functionally from the large colon?

Answer 7

• The small colon is specialized for water and electrolyte absorption.
• Unlike the large colon, it does not play a significant role in fermentation.

Question 8

How do horses get rid of methane/carbon dioxide?

Answer 8

Flatulence

Question 9

How are VFAs metabolised?

Answer 9

Energy source:
1. Acetate - used in liver, oxidised in most other cells to generate ATP, major source of acetyl CoA for lipid synthesis.
2. Propionate - substrate for gluconeogenesis.
3. Butyrate - energy production/ cellular homeostasis

Question 10

How do horses increase the pH of their large intestine?

Answer 10

1. Epithelial cells in the colon secrete bicarbonate (HCO₃⁻) into the lumen, neutralising acidic byproducts like VFAs and lactic acid.
2. Protons (H⁺) are absorbed along with VFAs by transporters like MCTs, which further reduces acidity.

Question 11

What is the role of the large intestine in water absorption?

Answer 11

The large intestine (cecum, large colon, small colon, rectum) absorbs the majority of water in the digestive system.

Question 12

Why do horses have a lower amylolyotic population in the fermentation chamber?

Answer 12

hCHO usually digested in small intestine in horse so fermentation slower as more celluloytic bacteria - proliferate slower.

Question 13

Compare large intestinal transit time between fore-gut and hind-gut fermenters and how this happens.

Answer 13

Hind-gut slower to allow fermentation to occur - separate compartments.

Question 14

What are the type of contractions in the caecum?

Answer 14

Segmental contractions and mass contractions (occur every 3-5 minutes).

Question 15

Define colic.

Answer 15

A clinical sign of abdominal pain.

Question 16

Define true colic.

Answer 16

Relates to gastro-intestinal pain

Question 17

Define false colic.

Answer 17

Relates to other abdominal organ pain (e.g. bladder, kidney, uterus etc)

Question 18

What is the most useful procedure in colic diagnosis?

Answer 18

Rectal examination

Question 19

What are haustral contractions in the equine colon?

Answer 19

Segmental contractions that occur in the sacculations (pouch-like segments) of the colon.

Question 20

Outline the movement of ingesta through the equine large intestine.

Answer 20

Caecum, right ventral colon, left ventral colon, left dorsal colon, right dorsal colon, transverse colon, small colon.