Chapter 41 Animal Nutrition and Digestion

Need to Feed Dietary categories Carnivore Herbivore Omnivore Animals are truly opportunistic eaters meaning occasionally they will eat something out of the norm when resources are scarce 3 nutritional needs 1. Fuel (chemical energy) 2. organic raw materials for biosynthesis 3. essential nutrients

Management of Energy Budget Nearly all an animal’s ATP generation is based on the oxidation of energy rich organic molecules – CHO, proteins, and fats Severe problems occur if budget is out of balance for long periods undernourishment – chronic deficiency in calories - stores of glycogen and fat are used up - body begins breaking down proteins - muscular atrophy - brain can become protein deficient overnourishment – excessive food intake - obesity is increasing problem - fat stores are compounded instead of being used for fuel - inheritance is a factor in obesity - hormone leptin may be a regulatory checkpoint to combat obesity

Animal’s Diet In order build complex molecules it needs to grow, maintain itself, and reproduce, animals must obtain organic precursors (carbon skeletons) from its food Essential nutrients – must be obtained in preassembled form because animals’ cell cannot make them from raw materials Ex: Vitamin C malnourishment – missing one or more essential nutrients 4 classes of essentials: 1. essential amino acids – 20 in diet; 10 naturally made 2. essential fatty acids – rarely deficient 3. vitamins water soluble – B complex, Folic acid, C fat soluble – A, D, E, K 4. minerals - calcium, phosphorus, iron, iodine, sodium

Stages of Food Processing The 4 stages of food processing: 1. Ingestion – eating; brings in large polymers that need to broken down for use 2. Digestion – mechanical and chemical break down of polymers into monomers the body can absorb *enzymatic hydrolysis- adding water to break bonds of macromolecules in food 3. Absorption – uptake of small molecules into bloodstream 4. Elimination – passing of undigested material out of body

Digestive System Peristalsis – rhythmic waves of contraction that moves food down esophagus; smooth muscle control Sphincters – ring like valves that act as junctions between specialized regions of digestive tube Accessory glands in digestion: a. Salivary glands – digestive enzymes b. Pancreas – digestive enzymes and buffer c. Liver – production of bile d. Gallbladder – storage and release to bile to break up fats Accessory to digestion because no food passes through these organs

Digestive System Mouth - will mechanically and chemically break down food particles - Food in mouth will stimulate a reflex that causes saliva to be released by salivary glands Saliva contains – - mucin- glycoprotein that coats the lining of mouth - buffers to prevent tooth decay - antibacterial agents - Amylase that hydrolyzes starch and glycogen

Digestive System Mouth pharynx – region of throat that is the junction between trachea and esophagus epiglottis- cartilaginous flap that covers the opening to trachea Esophagus – connects the mouth to stomach no digestion takes place; peristalsis

Ingestion

Digestive System Stomach - stores food and begins digestion - elastic walls expand when food enters - mechanical action of smooth muscles churn contents or chyme - gastric juice (HCl) mixes and dissolves food particles; kills bacteria present with food - pepsin – enzyme in gastric juice that will hydrolyze proteins

Early Digestion

Digestive System Small Intestine 3 sections: 1. Duodenum – mixes juices and bile from pancreas, liver, and gallbladder 2. Jejunum – absorption of nutrients 3. Ileum – absorption of nutrients and water

Enzymatic digestion

Digestive System Large Intestine - cecum is a pouch like extension of intestine - contains appendix- dispensible organ contains white blood cells that may aid in immunity/ microbial breakdown *Main function of colon is absorption of water and any useful remaining nutrients Rectum – terminal portion of colon

Evolutionary Adaptations Dentition, or assortment of teeth, has greatly contributed to success of vertebrate class - utilization of different shaped teeth for particular types of food or modes of nutrition Expandable stomachs allowing large portions of food and long periods between meals Symbiotic bacteria in alimentary canals Ruminants – 4 chambered stomach for digestive of herbivorous material *rumen, reticulum, omasum, & abomasum

Adaptations