Nutrition of Animal

Nutrition of Animal

Learning outcomes:

1. Nutritional requirements of animals
2. Diverse adaptations for obtaining and processing food

The Need to Feed

1. Every meal reminds us that we are heterotrophs, dependent on a regular supply of food
2. In general, animals fall into three categories:
a. Herbivores eat mainly autotrophs (plants and algae)
b. Carnivores eat other animals
c. Omnivores regularly consume animals as well as plants or algal matter
3. An adequate diet must satisfy three needs:
a. Fuel for all cellular work
b. Organic raw materials for biosynthesis
c. Essential nutrients, substances that the animal cannot make for itself
4. Main feeding mechanisms: suspension feeding, substrate feeding, fluid feeding, bulk feeding

Homeostatic mechanisms manage an animal’s energy budget

Nearly all of an animal’s ATP generation is based on oxidation of energy-rich molecules: carbohydrates, proteins, and fats

Glucose Regulation as an Example of Homeostasis

1. Animals store excess calories as glycogen in the liver and muscles and as fat
2. Glucose is a major fuel for cells
3. Hormones regulate glucose metabolism
4. When fewer calories are taken in than are expended, fuel is taken from storage and oxidized

Caloric Imbalance

1. Undernourishment occurs in animals when their diets are chronically deficient in calories
2. Overnourishment, or obesity, results from excessive intake, with excess stored as fat

Obesity as a Human Health Problem

1. The World Health Organization now recognizes obesity as a major global health problem
2. Obesity contributes to a number of health problems, including diabetes, cardiovascular disease, and colon and breast cancer
3. Researchers have discovered several of the mechanisms that help regulate body weight
4. Over the long term, homeostatic mechanisms are feedback circuits that control the body’s storage and metabolism of fat
5. Hormones regulate long-term and short-term appetite by affecting a “satiety center” in the brain
6. satiety center - a group of cells in the ventromedial hypothalamus that when stimulated suppress a desire for food

Obesity and Evolution

1. The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was a means of survival
2. A species of birds called petrels become obese as chicks due to the need to consume more calories than they burn

An animal’s diet must supply carbon skeletons and essential nutrients

1. An animal must obtain carbon skeletons from its food to build complex molecules
2. Besides fuel and carbon skeletons, a diet must supply essential nutrients in preassembled form
3. A malnourished animal is missing one or more essential nutrients in its diet

Essential Amino Acids

1. Animals require 20 amino acids and can synthesize about half from molecules in their diet
2. The remaining amino acids, the essential amino acids, must be obtained from food in preassembled form
3. A diet that provides insufficient essential amino acids causes malnutrition called protein deficiency
4. Most plant proteins are incomplete in amino acid makeup
5. Individuals who eat only plant proteins need to eat a variety to get all essential amino acids
6. Some animals have adaptations that help them through periods when their bodies demand extraordinary amounts of protein

Essential Fatty Acids

1. Animals can synthesize most of the fatty acids they need
2. The essential fatty acids are certain unsaturated fatty acids
3. Deficiencies in fatty acids are rare

Vitamins

1. Vitamins are organic molecules required in the diet in small amounts
2. 13 vitamins essential to humans have been identified
3. Vitamins are grouped into two categories: fat-soluble (A, D, E, K) and water-soluble
4. They can serve as coenzymes or parts of coenzymes

Minerals

Minerals are simple inorganic nutrients, usually required in small amounts