Overview
This lecture covers animal nutrition and digestion, focusing on differences between ruminant and non-ruminant digestive systems and their anatomical structures.
Animal Nutrition and Digestion
- Digestion is the process of breaking down food into nutrients absorbable in the bloodstream.
- Both animals and humans carry out digestion, but focus here is on animals.
The Alimentary Canal
- The alimentary canal is the passage food takes through the body, from mouth to anus.
- It absorbs water and excretes undigested food.
Ruminant Digestive System
- Ruminants (e.g., cows, sheep) have a complex stomach with four compartments: rumen, reticulum, omasum, abomasum.
- The alimentary canal includes mouth, esophagus, four stomach compartments, small intestine (long), and large intestine.
- The rumen contains papillae for absorbing volatile fatty acids from microbial digestion.
- Reticulum has a honeycomb structure and forms food boluses for rumination (chewing the cud).
- Omasum has many folds to squeeze water from food before it enters the abomasum.
- Abomasum is the "true stomach," producing hydrochloric acid and gastric enzymes.
Non-Ruminant Digestive System
- Non-ruminants (e.g., pigs, chickens) have a single, simple stomach (true stomach).
- The pig’s alimentary canal includes mouth, esophagus, stomach, small intestine (duodenum, jejunum, ileum), and large intestine (colon, rectum, anus).
- The chicken’s canal includes mouth, esophagus, crop, gastric complex (proventriculus and gizzard), small intestine, large intestine, rectum, and cloaca.
Digestion Process: Ruminants vs Non-Ruminants
- Mechanical digestion: breaking food into smaller pieces (chewing, muscular contractions).
- Chemical digestion: enzymes and acids break down food into basic chemicals.
- In the mouth, saliva contains salivary amylase that starts breaking down starch into maltose.
- In the stomach, hydrochloric acid and pepsin break down proteins into peptides.
- In ruminants, microbes in the rumen aid in digesting fibrous plants.
Differences Across Life Stages
- Young ruminants have a large abomasum and undeveloped fore-stomachs; mature ruminants have a large rumen.
- As young ruminants start eating solid food, the rumen develops and increases in size.
Key Terms & Definitions
- Alimentary Canal — the entire digestive tract from mouth to anus.
- Ruminant — an animal with a four-compartment stomach for digesting fibrous food.
- Non-ruminant — an animal with a single-compartment (simple) stomach.
- Rumen — the first and largest stomach compartment in ruminants, for microbial digestion.
- Reticulum — the second stomach compartment, with a honeycomb structure, forms food boluses.
- Omasum — the third compartment with folds that absorb water.
- Abomasum — the fourth compartment, functioning as the true stomach.
- Bolus — a ball of chewed food.
- Rumination — the process of regurgitating and re-chewing food (chewing the cud).
- Peristalsis — wave-like muscle contractions that move food through the digestive tract.
- Papillae — tiny projections in the rumen that absorb nutrients.
Action Items / Next Steps
- Leave your email to receive revision questions and memos.
- Engage with the instructor for further questions or clarifications.