Chapter 41 Animal Nutrition

Nutritional requirements Undernourishment: caloric deficiency Overnourishment (obesity): excessive food intake Malnourishment: essential nutrient deficiency Essential nutrients: materials that must be obtained in preassembled form Essential amino acids: the amino acids that must be obtained in the diet (Arginine, Histidine – Infants) Essential fatty acids: unsaturated fatty acids Vitamins: organic coenzymes Minerals: inorganic cofactors

Food types/feeding mechanisms Opportunistic Herbivore: eat autotrophs Carnivore: eat other animals Omnivore: both Feeding Adaptations Suspension-feeders: sift food from water (baleen whale) Substrate-feeders: live in or on their food (leaf miner) (earthworm: deposit-feeder) Fluid-feeders: suck fluids from a host (mosquito) Bulk-feeders: eat large pieces of food (most animals)

Overview of food processing 1-Ingestion: act of eating 2-Digestion: process of food break down enzymatic hydrolysis intracellular: breakdown within cells (sponges) extracellular: breakdown outside cells (most animals) alimentary canals (digestive tract) 3- Absorption: cells take up small molecules 4- Elimination: removal of undigested material

Mammalian digestion Peristalsis: rhythmic waves of contraction by smooth muscle Sphincters: ring-like valves that regulate passage of material Accessory glands: salivary glands; pancreas; liver; gall bladder

Mammalian digestion Oral cavity salivary amylase bolus Pharynx epiglottis Esophagus Stomach gastric juice pepsin/pepsinogen (HCl) acid chyme pyloric sphincter

Figure 41.3 Homeostatic regulation of cellular fuel STIMULUS: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood STIMULUS: Blood glucose level drops below set point. When blood glucose level rises, a gland called the pancreas secretes insulin, a hormone, into the blood. 1 Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops. 2 When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin. 3 Glucagon promotes the breakdown of glycogen in the liver and there lease of Glucose into the blood,increasing blood glucose level. 4

Figure The duodenum LiverBile Acid chyme Stomach Pancreatic juice Pancreas Intestinal juice Duodenum of small intestine Gall- bladder

Mammalian digestion Hormonal Action: Gastrin food---> stomach wall ---> gastric juice Enterogastrones (duodenum) 1-Secretin acidic chyme---> pancreas to release bicarbonate 2-Cholecystokinin (CCK) amino/fatty acids---> pancreas to release enzymes and gall bladder to release bile Large intestine (colon) Cecum Appendix Feces Rectum/anus

Figure Hormonal control of digestion Amino acids or fatty acids in the duodenum trigger the release of cholecystokinin (CCK), which stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder. Liver Gall- bladder CCK Entero- gastrone Gastrin Stomach Pancreas Secretin CCK Duodenum Key Stimulation Inhibition Enterogastrone secreted by the duodenum inhibits peristalsis and acid secretion by the stomach, thereby slowing digestion when acid chyme rich in fats enters the duodenum. Secreted by the duodenum, secretin stimulates the pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach. Gastrin from the stomach recirculates via the bloodstream back to the stomach, where it stimulates the production of gastric juices.

Mammalian digestion Small intestine duodenum bile Intestinal digestion: a-carbohydrate b-protein c- nucleic acid d-fat

Mammalian digestion Villi / microvilli Lacteal (lymphatic) Chylomicrons (fats mixed with cholesterol) Hepatic portal vessel

Evolutionary adaptations Dentition: an animal’s assortment of teeth Digestive system length Symbiosis Ruminants