Notes: Animal Solutions to Life – Feed the Animal (Comprehensive Study Notes)

Administrative and access details

• This class is being recorded for educational use, revision and for students unable to attend the live session.
• Recording content includes educator audio, video, main screen presentation, video clips, guest presenters, class activities, and may capture audio and video of participants.
• Access: The recording will be available through Moodle and should only be accessed by students enrolled in this unit.
• Privacy note: Do not share, reproduce, or distribute recordings.
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Acknowledgement and context

• Acknowledgement: We acknowledge the people of the Kulin Nations on whose land we are gathered today and pay respect to their Elders, past and present.
• Course title: Animal Solutions to Life: Feed the Animal; Presenter:Assoc Prof Matthew Piper; Topic: Nutritional Physiology.
• Model organism mentioned: Drosophila melanogaster.

Course context and structure

• Context: Evolving life involves Natural selection, fossils, and human evolution.
• Focus areas: Animal solutions to life include four interrelated stages:
  • Plan an animal
  • Move the animal
  • Feed the animal
  • Make more animals
• Reference slide framing: The workshop discusses how life plans, moves, feeds, and reproduces, linking to nutritional physiology and ageing.

Wellbeing and support

• If you have concerns about eating behaviours or body image, consider:
  • Monash University Health Service
  • The Butterfly Foundation

Module overview and organism focus

• Module: PiperLab nutritional physiology & ageing; Model organism cited: Drosophila melanogaster.
• Theme: How very different organisms in different environments have very similar nutritional needs; relate food composition to major molecular classes; describe digestive processes; distinguish adaptations in carnivores, omnivores, herbivores.

Learning outcomes

1) Explain how very different organisms in very different environments have very similar nutritional needs.
2) Relate the nutritional composition of foods to the major classes of molecules that constitute biomass.
3) Describe each of the major mechanical and chemical digestive processes.
4) Distinguish the major adaptations for nutrient acquisition in carnivores, omnivores, and herbivores.

Biomass building blocks: elements and macromolecules (background)

• Key macromolecules in biomass:
  • Proteins:
  • Elements: ext{C, H, N, O, S}
  • Carbohydrates:
  • Elements: ext{C, H, O}
  • Fats (lipids):
  • Elements: ext{C, H, O}
  • Nucleic acids:
  • Elements: ext{C, H, N, O, P}
  • Minerals (inorganic components)
• Autotrophs vs. Heterotrophs:
  • Autotrophs produce biomass from inorganic sources; heterotrophs obtain biomass via consumption of other organisms.
• Relevance: Major elements and molecules constitute the basis of biomass and energy for living systems.

Adapting to nutritional mismatches (background)

• Concept: Nutritional supply varies; organisms exhibit physiological and behavioural adaptations that impact evolutionary fitness.
• Process: Variation in supply drives adaptations that enable biomass growth and reproduction.
• Outcome: Organisms aim to balance intake with the needs to build biomass and reproduce.

Major points for today’s workshop

• 1) What makes up a body?
• 2) Physiological adaptations to obtain nutrients
• 3) Behavioural adaptation: homeostatic appetite control

What makes up a body? biomass composition activity

• Exercise prompt: Rank the components that make up the human body by biomass from highest to lowest proportion.
• Common educational takeaway (poll): Water is typically a large fraction; followed by proteins, carbohydrates, fats, minerals in many biological contexts. The exact ranking depends on the organism and body composition.
• Poll access example: Pollev (web poll) link provided in class.

Digestive system: summarised anatomy and function

• Sponge (Porifera) digestion (intracellular+extracellular):
  • Structures: Osculum, Mesohyl, Porocytes, Choanocytes, Amoebocytes, Spongocoel, Epidermis, Water flow, Food capture.
  • Digestion modes:
  • Extracellular digestion occurs in the canal system.
  • Intracellular digestion occurs within archaeocytes/amoebocytes.
  • Associated features: Body stalk; Spicules; Gastrovascular tract is not typical of sponges (instead there is a water canal system).
• Nematode digestion: Mouth → Pharynx → Intestine → Anus.
• General note: Digestive strategies span from intracellular (simple animals) to extracellular (more complex guts).

Digestive nutrient targets by consumer type

• Herbivores, Carnivores, Omnivores: different nutrient acquisition strategies align with their diets and dentition (see below).

Dentition and mechanical digestion: Carnivore vs Herbivore comparisons

• Carnivores: Premolars for slicing meat; incisors for snipping; molars less pronounced; mechanical digestion geared toward tearing.
• Herbivores: Premolars less slicing emphasis; incisors for cutting; molars more pronounced for grinding; mechanical digestion geared toward plant tissue processing.
• Omnivores: Mixed dentition; capable of handling both plant and animal matter.

Digestive tract components and mechanical digestion (examples from avian/poultry anatomy)

• Mechanical digestion pathway in birds:
  • Crop → Esophagus (gullet) → Proventriculus → Gizzard → Large intestine → Cloaca/Vent → Small intestine.
• Summary of major organs involved:
  • Crop: storage; softens contents.
  • Proventriculus: glandular stomach; chemical digestion begins.
  • Gizzard: muscular grinding organ; mechanical breakdown.
  • Liver: produces bile.
  • Pancreas: secretes digestive enzymes and bicarbonate.
  • Duodenum: primary site of enzymatic digestion.
  • Small intestine: enzymes (disaccharidases, aminopeptidases, carboxypeptidases) for final digestion; absorption occurs along the small intestine.
  • Gall bladder: stores bile; Bile salts aid fat digestion.
  • Pancreatic secretions include: ext{NaHCO}_3, ext{enzymes (amylase, trypsin, chymotrypsin, carboxypeptidase, nuclease, lipase)}
  • pH of stomach: approximately pH
    ightarrow 2 for acid hydrolysis; enzyme digestion includes activation (pepsinogen → pepsin).
• Secretions of the small intestine:
  • Enzymes such as disaccharidases, aminopeptidases, peptidases; aid disassembly of carbohydrates and proteins.
• Chemical digestion examples:
  • Pepsinogen → Pepsin in the stomach; proteolysis occurs under acidic conditions.

Getting help with digestion: microbial contributions (fermenters)

• Foregut fermenters: rumen, reticulum, omasum, abomasum (see below for functional roles).
• Hindgut fermenters: large intestine and/or cecum (fermentation occurs after absorption of simple nutrients).
• Foregut fermenter details:
  • Complex stomach with multiple compartments (rumen, reticulum, omasum, abomasum).
  • Microbial symbionts (protozoa, bacteria, fungi) ferment plant cell contents to produce volatile fatty acids (VFAs) that provide energy; digested bacteria can provide microbial protein.
  • Energy supply and protein supply come from VFAs and microbial protein, respectively.
• Hindgut fermenter details:
  • Digestive processing occurs primarily in the hindgut with microbial fermentation producing VFAs for energy; location of fermentation is in the caecum/colon.

Major points for today’s workshop (repeat with emphasis)

• 1) What makes up a body?
• 2) Physiological adaptations to get nutrients
• 3) Behavioural adaptation: homeostatic appetite control

Activity 2: Plan a Diet

• Group activity (4–6 people): half plan ultra-processed diet, half plan minimally processed diet.
• What to produce:
  • Write the diet in a provided table
  • Calculate total amounts of protein, carbohydrates, and fats per meal and for the day
• Example items shown in the activity (illustrative list): burger, chips, apple, avocado, berries, chicken, cereal, donuts, coffee, milk, orange juice, eggs, nuts, salmon, pizza, doughnut, etc.
• Energy and macronutrient data:
  • Foods have energy contributions measured in kJ (kJ). Examples shown include categories such as protein, carbohydrate, and fat contributions to each item; total daily energy is computed as the sum of meal energies.
  • In the provided class materials, sample totals include figures such as the following (illustrative, from the activity):
  • Ultra-processed daily energy totals: around 6{,}423 ext{ kJ}
  • Minimally processed daily energy totals: around 5{,}419 ext{ kJ}
  • The exercise also requires listing per-meal protein, carbohydrate, and fat contributions and summing to daily totals.

Activity 2: Comparisons of Diets (data interpretation)

• Diet type to circle: Ultra-processed or Minimally processed.
• Daily diet components tracked: Breakfast, Lunch, Dinner, Snack, with totals for Protein, Carbohydrates, Fats, and Total energy (kJ).
• Example outcomes shown in the materials indicate total daily energy values such as 6423 ext{ kJ} (ultra-processed) and 5419 ext{ kJ} (minimally processed) in some iterations; exact values depend on the chosen meals and portion sizes.
• The exercise includes compiling a table of daily totals and comparing energy and macronutrient composition between diet types.

Summary visuals and interpretations from the diet activity

• Key takeaway: Ultra-processed diets tend to be energy-dense with high palatability and relatively low satiety; minimally processed diets tend to be less energy-dense and may lead to different fat/protein balance outcomes.
• The concept of energy density and macronutrient balance is central to nutrient-dense vs. energy-dense dietary patterns.

Nutrient balancing and appetite control (conceptual framework)

• Higher organisms balance diet using behavioural strategies to align intake with nutrient needs.
• Nutrient space model (Raubenheimer & Simpson):
  • Nutrients are represented in a multi-dimensional space (e.g., Protein P, Carbohydrate C, Fat F).
  • Intake Target (IT): the organism’s desired intake vector (P, C, F*).
  • Actual intake vector: (P, C, F) from consumed foods.
  • Distance to target: d = ext{distance}((P, C, F), (P^, C^, F^*)) (e.g., Euclidean distance) which the organism attempts to minimize by adjusting intake.
• Intake target considerations: protein often governs appetite and satiety in primates, including humans; imbalanced diets can push the organism to adjust consumption to meet protein needs or balance carbohydrate/fat intake.
• Practical implication: When facing dietary imbalance, strategies include prioritising protein or prioritising carbohydrate/fat depending on deficit or surplus, aiming to move toward the intake target.

Nutrient space and practical guidance (from the slides)

• If Carbohydrate + Fat deficit and Protein excess: Prioritise Protein.
• If Protein deficit and Carbohydrate + Fat excess: Prioritise carbohydrate/fat intake to rebalance.
• The objective is to achieve a balanced nutrient intake that supports growth, maintenance, and reproduction rather than just maximizing energy intake.

Target of Rapamycin (TOR) signalling and ageing (concepts)

• TOR is a central cellular pathway that integrates amino acid availability to regulate growth, metabolism, and ageing.
• Rapamycin is an inhibitor of TOR signalling and has been studied as a potential anti-ageing intervention.
  • Experimental comparison shows survival differences with rapamycin treatment at different concentrations (e.g., 0 µM vs 200 µM) in model organisms.
• Practical context: TOR signalling links nutrient sensing to lifespan; modulating TOR (e.g., via rapamycin) can influence ageing processes in model systems.

The Dog Aging Project (contextual example)

• The Dog Aging Project is a large-scale research initiative to study healthy lifespan in dogs, involving dogs of all breeds and ages, owners, veterinarians, researchers, and volunteers.
• Aim: identify biological and environmental factors that maximize healthy longevity in dogs over a ten-year study period.

Ethical, philosophical, and practical implications

• Ultra-processed foods: industry composition, palatability, satiety, and nutritional value; debate about health implications and dietary guidelines.
• “Human rule of compromise?”: Protein tends to govern appetite and satiety in primates, including humans; balancing macronutrients may require dietary choices beyond caloric reduction alone.
• Practical health considerations: when concerns about eating behaviours or body image arise, seek professional guidance (health services, mental health resources).

Key equations and concepts (LaTeX-formatted)

• Energy from macronutrients (kJ):
  E_{kJ} = 4.184 imes igl(4P + 9F + 4Cigr)
  where P, F, C are grams of protein, fat, and carbohydrate, respectively.
• Protein to carbohydrate+fat ratio (nutritional balance):
  R = rac{P}{C + F}
• Distance to intake target in nutrient space (conceptual):
  d = igl(P - P^, ext{ } C - C^, ext{ } F - F^igr)^{2} ight)^{1/2} or more explicitly, d = igl(P - P^igr)^{2} + igl(C - C^igr)^{2} + igl(F - F^igr)^{2}
  ight)^{1/2}
• Intake Target (IT): a vector IT = (P^, C^, F^*) representing the organism’s nutritional goals.

Connections to foundational principles

• Evolution and natural selection underpin adaptive nutritional strategies in both physiology and behaviour.
• Digestive anatomy (e.g., foregut vs hindgut fermentation, sponge digestion, vertebrate GI tract) demonstrates how organisms optimize nutrient extraction from available resources.
• The balance between energy intake and nutrient adequacy shapes growth, reproduction, ageing, and health outcomes.
• Ethical and practical implications emphasize real-world decision-making around diet, wellbeing, and responsible consumption of processed foods.

Quick recap of key takeaways

• Nutritional needs are conserved across diverse life forms, yet strategies differ by environment and diet type (carnivore, omnivore, herbivore).
• Digestive systems involve both mechanical and chemical processes, with variations across taxa (e.g., crop and gizzard in birds; foregut/hindgut fermentation in ruminants and other mammals; extracellular vs intracellular digestion in simple animals such as sponges).
• Diet planning exercises illustrate how different food choices impact macronutrient balance and total energy, highlighting the contrast between ultra-processed and minimally processed diets.
• Nutrient balancing frameworks (nutrient space and intake targets) explain how organisms adjust intake to meet protein and energy needs, potentially overriding simple caloric optimization.
• TOR signalling links nutrient availability to ageing; interventions like rapamycin in model systems offer insights into the biology of ageing and longevity.
• Practical resources for wellbeing are available if concerns arise; ethical dietary choices have broad real-world implications.

Questions to check understanding

• What are the major macromolecules that constitute biomass, and what elemental make-up do they share?
• Differentiate foregut and hindgut fermenters in terms of digestion and energy sources.
• How do dentition and mechanical digestion reflect an animal’s diet (carnivore vs herbivore vs omnivore)?
• Explain the concept of nutrient space and intake target. How would you respond if protein intake is deficient but energy intake is high?
• What role does TOR signalling play in ageing, and how might rapamycin affect lifespan?

References and further reading (implicit from slides)

• Raubenheimer, D., & Simpson, S.J. (2005). Nutrient balancing in an omnivore: protein governs appetite and satiety in primates (including humans). Obesity Reviews.
• Simpson, S.J., Raubenheimer, D. (2005). The food regulation system and nutrient balancing in animals.
• Raubenheimer, D., Johnson, C.A., Rothman, J.M., Clarke, D., Swedell, R. (2013). Nutrient balancing in primates. PLoS ONE.
• Dog Aging Project: overview and participation information.
• General vertebrate and invertebrate digestive physiology references (as implied by slide content).