Animal Nutrition

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

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

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

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

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

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)

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

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

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

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

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

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.