6.4: Understanding Different Digestive Systems Activity

Teach Back Instructions \(\PageIndex{1}\)

1. Arrange participants into five groups.
2. Assign each group one of the following:
   • Cow (Ruminant)
   • Pig (Monogastric/Omnivore)
   • Horse (Hindgut Fermenter)
   • Bird/Chicken (Avian)
   • Ruminant and Non-ruminant
3. Conduct Research: Use course resources and reliable outside sources to gather detailed information. Your group must become the experts on your assigned topic. (Cite any outside sources.)
   • Focus Areas: Anatomy (specific organs), Physiology (how digestion occurs), and unique adaptations.
   • Key Details to Include: The food's journey, the types of feed consumed, and the role of key organs.
   • Compare Systems: Briefly compare your animal's system to the others, noting similarities and differences.
4. Develop a Teaching Strategy: Outline how your group will teach the material. How do your group members like to learn? What about this topic drives your group's curiosity? What gets your group speaking about and interacting with a topic? Use pictures and/or diagrams to illustrate the food's journey from entry to exit. (Cite your image sources.)
5. Each group will deliver a clear, engaging, and thorough presentation to teach the rest of the class about your assigned digestive system.
   • Goal: Your presentation should be comprehensive enough that your peers understand this type of digestive system, if it is their only source of information on the topic, and even if they aren't taking this class.
   • Engagement: Use your visual aids effectively and ensure every group member participates in the teaching process.
6. After your presentation, your group will facilitate a brief Q&A session.
   • Be prepared for questions on complex concepts, unique features, and comparisons with other systems.
   • Or use this time to clarify any confusing concepts.
7. Before the end of class, each participant will complete a brief written reflection based on the presentations.
   • Submission: This reflection must be turned in before leaving class today.
   • Reflection Prompts: On a separate sheet of paper, address the following:
8. What was the most surprising or new detail you learned about the digestive system of an animal that wasn't your own?
9. Briefly describe a key anatomical or physiological difference between the ruminant and the horse/hindgut fermenter digestive systems, as presented today.

Key Points to Include

Avians (Poultry)

• Key Features: Lack teeth and have specialized upper GI tract organs.
• Crop: Stores and moistens food; limited fermentation occurs.
• Proventriculus (Glandular Stomach): Secretes HCl and pepsin (gastric juices).
• Gizzard (Ventriculus): Highly specialized, muscular organ for grinding food; no enzyme secretion here.
• Ceca: Two large ceca digest fiber near the junction of the small and large intestine.
• Cloaca: Common orifice for waste elimination, copulation, and egg laying.

Ruminant (e.g., Cow)

• Key Features: Alloenzymatic digestion (relying on microorganisms) in a complex, four-compartment stomach. Utilizes roughage and fiber extensively.
• Rumen (Largest): Site of anaerobic bacterial fermentation. Microbes produce VFAs (primary energy source, 50−70% of needs), bacterial protein, and vitamins (K and water-soluble).
• Reticulum (Honeycomb Lining): Pacemaker for rumen contractions and helps move food.
• Omasum (Many Folds): Absorbs water, electrolytes, and VFAs; reduces particle size.
• Abomasum (True Stomach): Glandular; secretes HCl and pepsin to digest both feed and microbial protein.
• Rumination (Chewing Cud): Regurgitation and re-chewing of food to increase surface area for microbial digestion.
• Eructation: Belching of fermentation gases.
• Trade-offs: Enables digestion of poor-quality feeds but can decrease the value of high-quality feeds due to fermentation energy cost.

The Horse (Hindgut Fermenter)

• Key Features: Monogastric stomach, but the majority of microbial digestion occurs in the hindgut (cecum and large colon).
• Prehension: Uses teeth, flexible upper lip, and tongue. Saliva is purely for lubrication (no enzymes).
• Stomach: Smaller capacity and reduced muscular activity compared to other mammals, increasing susceptibility to digestive disorders (e.g., colic).
• No Gallbladder: Evolved as continuous grazers; no need for bile storage.
• Cecum & Large Intestine: Account for over 60% of total gut capacity. Bacteria here ferment fiber into Volatile Fatty Acids (VFAs), the main energy source for forage diets.
• Protein Limitation: Bacterial protein synthesized in the hindgut is poorly absorbed as it is beyond the primary absorption site (small intestine).

Pig (Monogastric/Omnivore)

• Key Features: Monogastric system with one stomach. Primarily relies on enzymatic digestion in the stomach and small intestine.
• Stomach: Contains enzymes (e.g., pepsin) typical of monogastrics. Salivary amylase is present but minimally active due to short retention and low stomach pH.
• Small Intestine: Site of most protein and fat digestion and absorption.