Animal Phys Digestion

Food needed for

Energy (metabolic fuel, heat), Growth (raw materials used to build macromolecules, etc.), Reproduction (need energy & raw materials).

Principal body components

water = 60% of body and 60-95% of cells

Protein = ½ of organic matter

Lipids = fatty acids, fuel, cushioning, protection, energy reserve. Anhydrous lightweight.

Minerals = metalloproteins, enzymes

Nucleic acids = DNA, RNA

Carbohydrates = mostly structural, used up for metabolism as quick energy

Feeding

Animals evolve specific feeding apparatus’ and behaviors to meet their nutritional demands through specific foods suited to them. Animals make choice in food to try to balance nutrition to meet their needs (spider lipid vs carb example).

Ex. type of beak in birds. Radula in snail.

Digestive Breakdown

enzymes produced by animal breaks down food ingested.

Fermentative breakdown

heterotrophic microbes in animals help breakdown food through fermentation (symbiosis).

Absorption

transport proteins help absorb products of digestion and fermentation.

Nutrients Acquired

Nutrients delivered to cells after absorption. Triggers negative feedback to show animals nutritional requirements are being met.

Foregut fermenters - Ruminants

Foregut = esophagus and stomach.

Ruminant mammals - herbivores

heterotrophic, fermenting microbes live in non-acidic fluid of enlarged rumen and help breakdown plant material.

Rumen - first chamber of stomach where fermentation takes place

Reticulum - 2nd chamber, 2nd largest.

Omasum - 3rd chamber, leaf-like folds, allow liquid and fine particle to filter through.

Abomasum - 4th chamber “true stomach”. Secretes acid and digestive enzymes.

Pylorus - valve at bottom of stomach, controls entrance into intestines.

Intestines

Often regurgitate matter from rumen to be rechewed and swallowed.

Digastric Digestion in Ruminants

Smooth muscle in rumen contract to mix food and bacteria in churning manner.

Microbial fermenters breakdown cellulose to make short chain organic acids while releasing methane and CO2. The short chain organic acids are digested by animal.

Microbial fermenters breakdown protein into organic acids and ammonia.

Microbes use ammonia (from feed breakdown and/or urea from liver of animal) and organic acids (from feed breakdown) for protein synthesis. The bacterial protein is digested by animal.

Midgut fermenters

Tilapia, carp, catfish.

Food fermented and nutrients absorbed in small intestine.

Hindgut fermenters

Rabbits, elephants, horses, rhinos, apes, rodents, some turtles and lizards, some herbivorous birds.

Occur in hindgut (large intestine and cecum). Enlarged cecum and/or enlarged colon

Large intestine does not digest and absorb nutrients, except water and some fermentation products. Carbohydrates and cellulose breakdown to produce short-chain fatty acids and diffuse through gut wall into blood wherever they occurred in gut.

Microbes plus other nutrients must be reingested through feces to absorb nutrients (vitamins & amino acids) in small intestine.