Rumen Development and Gut Motility

How do stomach compartments change in relative capacity as ruminant grows?

Neonate: abomasum largest.

Transition: rumen grows rapidly.

Adult: rumen largest, then omasum, abomasum, reticulum.

What are the sources of energy for fetus, calf, and cow?

Fetus: glucose via placenta. Calf: lactose from milk. Cow: VFAs from rumen fermentation

What is colostrum and why is it important?

First milk; rich in immunoglobulins, fat, protein, vitamins.

Provides passive immunity, energy, laxative effect

When to feed colostrum?

Within 1–2 hours after birth; gut closure by ~24 hours. Feed 10% of body weight in first 6 hours.

• - RICH IN: Immunoglubulins; Protein; Fat-soluble vitamins; Minerals; Carotenoids

What is innate immunity?

Born with it; non-specific; physical barriers, phagocytes

What is passive immunity?

Acquired from mother; temporary; colostrum immunoglobulins

What is active immunity?

Body produces own antibodies after exposure; vaccination or infection

What is rennin and what is its function?

Enzyme in abomasum of young ruminants; curdles milk (casein → paracasein) so it stays longer for digestion.

Why is the esophageal groove important for young ruminants?

Directs milk from esophagus → omasum → abomasum, bypassing rumen; prevents fermentation of milk.

What are the two types of scours and how are they caused?

Nutritional (overfeeding, irregular feeding, poor milk replacer) and infectious (bacteria, viruses, protozoa).

Why is concentrate important for young ruminants?

Stimulates rumen development via VFA production; increases rumen capacity; establishes microbes; prepares for weaning.

How does concentrate influence rumen development?

Fermentation → VFAs → papillae lengthening and increased density. Butyrate fuels rumen epithelium.

What are the functions of rumen contractions?

Mix digesta with microbes, bring feed in contact with papillae, move digesta, eructation, rumination.

What are primary contractions?

~1–2 per minute; mixing, eructation, propulsion

A-wave: Moves in the caudal/backward direction

What are secondary contractions?

~1 per 2–3 minutes; extra mixing, eructation, rumination

B-wave: Moves cranially/forward. Usually follows primary contractions

What are the functions of biphasic reticulum contractions?

Two phases; extra reticulum contraction; helps move digesta

What are the functions of triphasic reticulum contractions?

Three phases; associated with rumination; regurgitation.

Has an extra contraction and creates negative pressure in the esophagus

What stimulates rumen contractions?

Physical (fiber, fill), chemical (VFAs, CO₂, pH), neural (vagus), hormonal (gastrin, motilin)

What stimulates rumination?

Fiber/roughage, large particle size, rumen fill, time of day (night/rest). Low pH inhibits

What are the main gases of eructation?

CO₂ (~60–70%), CH₄ (~20–30%), N₂ (~5–10%), H₂ (trace), H₂S (trace)

What is free gas bloat?

Gas trapped in free bubble; can't eructate. Caused by obstruction, vagus nerve damage, posture

What is frothy bloat?

Gas trapped in stable foam; can't escape. Caused by high legume (alfalfa), high grain, soluble proteins

What is high grain bloat?

Rapid fermentation → excess gas + foam

What is legume bloat?

Soluble proteins + saponins stabilize foam

What is the function of omasal contraction?

Regulates flow from reticulum to abomasum; helps absorb water; prevents large particles from passing.

What slows down abomasal motility?

High acidity (low pH), fat content, duodenal distension, sympathetic nervous system.

What is the function of SI motility and factors affecting it?

Mix chyme with enzymes, move digesta, absorb nutrients. Affected by vagus (↑), sympathetic (↓), hormones (CCK, secretin, gastrin), diet, disease

What is the function of LI motility and factors affecting it?

Absorb water/electrolytes, move feces, some fermentation. Affected by fiber (↑), water content, vagus (↑), sympathetic (↓), disease

Peristalsis: Movement of digesta - Toward the end of the animal —> caudal movement

Anti-peristalsis: Movement - Toward the head —> cranial movement

Segmentation

Rythmic contractions of adjacent sections of the gut