After studying this chapter you will be able to: Name the three nutritional needs that must be met by an animal’s diet; describe the four classes of essential nutrients; distinguish among undernourishment, overnourishment, and malnourishment; describe the four main stages of food processing;. | Chapter 41 Animal Nutrition Overview: The Need to Feed Every mealtime is a reminder that we are heterotrophs Dependent on a regular supply of food Figure In general, animals fall into one of three dietary categories Herbivores eat mainly autotrophs (plants and algae) Carnivores eat other animals Omnivores regularly consume animals as well as plants or algal matter Regardless of what an animal eats, an adequate diet must satisfy three nutritional needs Fuel for all cellular work The organic raw materials for biosynthesis Essential nutrients, substances such as vitamins that the animal cannot make for itself Animals feed by four main mechanisms Figure Baleen SUSPENSION FEEDERS Feces SUBSTRATE FEEDERS BULK FEEDERS FLUID FEEDERS Caterpillar Concept : Homeostatic mechanisms manage an animal’s energy budget Nearly all of an animal’s ATP generation Is based on the oxidation of energy-rich molecules: carbohydrates, proteins, and fats Glucose Regulation as an Example of Homeostasis Animals store excess calories As glycogen in the liver and muscles and as fat Glucose is a major fuel for cells Its metabolism, regulated by hormone action, is an important example of homeostasis Figure 1 When blood glucose level rises, a gland called the pancreas secretes insulin, a hormone, into the blood. 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 STIMULUS: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood STIMULUS: Blood glucose level drops below set point. Glucagon promotes the breakdown of glycogen in the liver and the release of glucose into the blood, increasing blood glucose level. 4 When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin. 3 When fewer calories are taken in than are expended Fuel is taken out of storage and oxidized Caloric . | Chapter 41 Animal Nutrition Overview: The Need to Feed Every mealtime is a reminder that we are heterotrophs Dependent on a regular supply of food Figure In general, animals fall into one of three dietary categories Herbivores eat mainly autotrophs (plants and algae) Carnivores eat other animals Omnivores regularly consume animals as well as plants or algal matter Regardless of what an animal eats, an adequate diet must satisfy three nutritional needs Fuel for all cellular work The organic raw materials for biosynthesis Essential nutrients, substances such as vitamins that the animal cannot make for itself Animals feed by four main mechanisms Figure Baleen SUSPENSION FEEDERS Feces SUBSTRATE FEEDERS BULK FEEDERS FLUID FEEDERS Caterpillar Concept : Homeostatic mechanisms manage an animal’s energy budget Nearly all of an animal’s ATP generation Is based on the oxidation of energy-rich molecules: carbohydrates, proteins, and fats Glucose Regulation as an Example of .
