Ruminant GIT 1.

Question 1

What is a ruminant?

Answer 1

-A ruminant is an animal that has a stomach with four complete cavities, which characteristically regurgitates undigested food from the rumen and masticates it at rest.
-The ruminant stomach is divided into four chambers:
1.) Rumen (80%).
2.) Reticulum (5%).
3.) Osmasum (8%).
4.) Abomasum (7%): true glandular stomach (analogous to the dog).
-Ruminants regurgitate undigested food from the rumen and masticate (chew) it when at rest.
-This is known as rumination (also colloquially known as chewing the cud).
-Rumination involves:
1.) Regurgitation.
2.) Remastication.
3.) Ensalivation.
4.) Reswallowing.

Question 2

How do ruminants digest food?

Answer 2

-Ruminants are grazers of voluminous, rich in fibre food, with relatively low digestibility (e.g., grasses).
-This plant cell material cannot be broken down effectively by the animal itself, so there is a need for:
1.) Microbial enzymes for fermentation.
2.) Optimal conditions that are anaerobic, with a pH of 6.5-7.0.
3.) A large vat to allow for hermentation and mechanical breakdown of food to occur as it is a long process– the rumen!

Question 3

Rumen?

Answer 3

-Largest compartment (fermentation vat).
-Occupies most of abdomen particularly LHS:
1.) Extends from the cardia (8th Rib) cranially to the pelvic brim caudally.
2.) From the abdominal roof dorsally to the floor ventrally.
3.) From the left body wall laterally across to the midline.
-Functions:
1.) Storage.
2.) Mechanical mixing and breakdown of digesta.
3.) Fermentation.
4.) Some absorption.
-Keratinized, stratified squamous, non-glandular.

Question 4

Reticulum?

Answer 4

-Cranial to rumen: faces the diaphragm.
-Between 6th to 9th intercostal space.
-Functionally linked to the rumen:
1.) Communicates over the ruminoreticular fold.
2.) Sometimes referred to together as ‘ruminoreticulum’.
-Often collects ingesta objects (e.g., wires).
-Close proximity to:
1.) Diaphragm.
2.) Pericardium (e.g., traumatic reticulates).
3.) Heart.
-Internal appearance: honeycomb plicae and papilla.
-Function: sorting ingesta for further chewing (rumination).
-Stratified squamous epithelia. Keratinized (protection and absorption).

Question 5

Omasum?

Answer 5

-Food ball-shaped: on the right-hand side.
-Entirely covered by the rib cage.
-Firmly attached to the rumen, reticulum, and abomasum.
-Interal laminae ‘bible pages’: Laminae covered in papillae.
-Functions:
1.) Absorbs volatile fatty acids, water, and electrolytes.
2.) Carries out additional fermentation.
3.) Regulates the flow of ingesta into the abomasum.
-Stratified squamous epithlium, keratinized.

Question 6

Abomasum True stomach?

Answer 6

-True glandular stomach.
-Analogous to a simple stomach.
-Piriform shaped.
-Ventral and slightly right of the midline in position.
-Functions:
1.) Enzymatic digestion of protein in food material.
-pH: 2-3.
-Columnar epithelia.

Question 7

Gastric Groove?

Answer 7

-A channel through the stomach following its lesser curvature, found in all domestic species.
-But ruminant has large rumen compartments?
-In ruminants, the gastric groove is divided into:
1.) Reticular groove (formerly oesophageal groove).
2.) Omasal groove.
3.) Abomasal groove.

Question 8

Reticular groove?

Answer 8

-Descends from the cardia over the right face of the reticulum down to the reticulo-omasal orifice.
-The groove is bound by spiral muscular fleshy lips which, when contract form a rub.
-Stimulated by:
1.) Suckling reflex.
2.) Presentation of milk.
3.) Chemical compounds in adults (e.g., copper sulphate).
-The muscular lips reflexively contract with suckling to form a tube.
-The tube channels the milk directly into the abomasum from proteolytic digestion.
-If milk enters the rumen it curdles and goes off.

Question 9

Development of the Rumen?

Answer 9

-Newborn calves:
1.) Solely ingest milk: no need for forestomachs.
2.) Abomasum is large.
3.) Forestomachs are small.
-Development of forestomachs:
1.) Stimulated by fibre feed.
2.) Papillary growth stimulated by volatile fatty acid production.
3.) Becomes larger than the abomasum by 2 months old.
4.) Development of the rumen completes by 6-12 months old.

Question 10

Spleen?

Answer 10

-Extends cranioventrally:
1.) Upper end lies at the dorsal ends of the last 2 ribs (12 and 13).
2.) Lower end lies at the 7th costochondral joint.
-Biopsy from the 11th intercostal space at the level of the tuber coxae.

Question 11

Small intestine?

Answer 11

-Duodenum (right of the midline):
1.) Descending.
2.) Ascending (connected to the small colon by the duodenocoloic fold).
-Jejunum:
1.) Within the supraomental recess.
2.) Suspended from the roof of the abdomen by the common dorsal mesentery.
-Ileum:
1.) Connected to the caecum by the ileocaecal fold.

Question 12

Large intestine?

Answer 12

-Caecum:
1.) Located in the upper right flank.
2.) Free end can be palpated per rectum.
-Colon:
1.) Ascending: proximal loop, spiral loop, and distal loop.
2.) Transverse.
3.) Descending.
-Rectum:
1.) Suspended by mesorectum.