1. Animal Nutrition

2. Animal Diets Animals have a variety of diets
Omnivore, carnivore, herbivore
Main purpose is for animals to take in the necessary calories to supply chemical energy
Need 4 essential nutrients
Essential amino acids
Essential fatty acids
Vitamins
Minerals

4. Dietary Deficiencies
Diets that do not meet these basic needs lead to undernourishment and malnourishment
To aid in attaining nutrition, animals often eat a variety of strange things like antlers of other animals or their own placenta
Dietary deficiencies have been implicated in a variety of diseases and birth defects
Folic acid / vitamins for prenatal care

5. Feeding Mechanisms
There are 4 main feeding mechanisms common to animals
Suspension Feeders
Substrate Feeders
Fluid Feeders
Bulk Feeders

6. Food Processing
Food processing involves ingestion, digestion, absorption, and elimination
Digestion is completed via mechanical and chemical digestion
Chemical digestion is completed using enzymatic hydrolysis
This breaks chemical bonds of macromolecules through the addition of water

7. Digestive Compartments
The ability of an animal to digest food without digesting itself is related to digestive compartmentalization
Intracellular Digestion
Food vacuoles and lysosomes within individual cells take care of digestion (pinocytosis and phagocytosis)
Ex: Sponges

8. Digestive Compartments
Extracellular Digestion
Breakdown of food in compartments that are continuous with the outside of the animal’s body
Includes gastrovascular cavity (one opening such as the hydra and flatworms) and alimentary canal (two openings such as earthworms, grasshoppers and birds)

9. Mammalian Digestion
Digestion begins in the oral cavity with both mechanical and chemical digestion
Via chewing and saliva. Saliva also contains amylase which hydrolyzes starch and glycogen
Swallowing allows the passage of bolus from the pharynx to the esophagus
Peristalsis “pushes” the bolus to the stomach

10. Mammalian Digestion
Stomach absorbs some nutrients, but primarily works in chemical and mechanical digestion
Can hold up to ~2 L
Gastric juice is secreted by the stomach for chemical digestion
Gastric Juice is composed of hydrochloric acid and pepsin, largely used to digest proteins
After digestion, the sphincter at the base of the stomach releases chyme into the small intestine

11. Mammalian Digestion
The small intestine is the primary site for enzymatic hydrolysis
Longest compartment at ~6 m long
Initial portion is duodenum where chyme mixes with digestive juices from pancreas, liver and gallbladder
These enzymes have several jobs including: making chyme less acidic and digestion of fats
The jejunum and ileum function in absorption of nutrients and water

13. Mammalian Digestion
The large intestine includes the colon, cecum and rectum
Colon is key in absorption of water (~90% of water that enters alimentary canal)
A portion of the human cecum is the appendix

14. Evolutionary Adaptations
Animals have a variety of adaptations to aid in their digestion
Specialized teeth for particular eating habits
Mutualistic adaptations with a variety of bacteria and other microorganisms
Specialization of cecum specific to the amount of cellulose ingested by the species

15. Homeostasis and Digestion
The digestive system plays a key role in homeostasis
Glycogen and insulin regulate blood sugar
Body stores energy in liver, muscle and fat for later use. If energy continues to be stored rather than used, obesity may result.
A variety of hormones regulate appetite to aid in regulating body fat.