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ANIMAL NUTRITION Chapter 41 Animals are heterotrophs Nutrition is not only the need for food, but also the need for specific food components. Require food for 2. 1. fuel (chemical energy) carbon for its own molecules 3. essential nutrients FUEL - ATP BIOSYNTHESIS ENERGY STORAGE Food Processing Ingestion Digestion Absorption Elimination Act of eating Process of breaking food down into molecules small enough for the body to absorb Take up small molecules from the digestive compartment Undigested material passes out of the digestive compartment Intracellular Extracellular Dietary Categories (represents the kind of food the animal usually eats) Herbivores Carnivores Omnivores Mainly eat plants and algae Eat other animals Consume animals as well as plants or algae Gorillas Sharks Cockroaches Cows Hawks Crows Hares Spiders Bears Snails Snakes Raccoons Humans Most animals are opportunistic – Eating foods that are outside their main dietary category Feeding Mechanisms Suspension (filter) feeders Substate feeders Fluid feeders Bulk feeders Sift small food particles from the water Live in or on their food source Suck nutrient rich fluids from a living host Eat relatively large pieces of food Clams Maggots Mosguitos Oysters Earthworms Leeches Most animals Baleen whales Hummingbirds Bees Feeding Mechanisms Suspension (filter) feeders Sift small food particles from the water Sponges Clams Oysters Baleen whales Feeding Mechanisms Substate feeders Live in or on their food source Maggots Earthworms Feeding Mechanisms Fluid feeders Suck nutrient rich fluids from a living host Mosguitos Leeches Hummingbirds Bees Feeding Mechanisms Bulk feeders Eat relatively large pieces of food Most animals Food Processing Ingestion Digestion Absorption Elimination Act of eating Process of breaking food down into molecules small enough for the body to absorb Take up small molecules from the digestive compartment Undigested material passes out of the digestive compartment Intracellular Extracellular Virtually all food, whether of plant or animal origin, consists of highly complex compounds that cannot be used without first being broken down to simpler compounds = digestion. CHOs, fats and proteins can all be used as fuel. Campbell; Fig. 9.19 Net Energy Value of Foods 4 kcal per gram for protein Amino acids 4 kcal per gram for CHO Simple sugars 9 kcal per gram for lipid Fatty acids Campbell; Fig.40.10 If the food intake exceeds the energy used, most animals store the surplus as fat, irrespective of the nature of the food. Net Energy Value of Foods 4 kcal per gram for CHO Fast Aerobic or anaerobic Storing glycogen also requires storing water Simple sugars 9 kcal per gram for lipid Slower Aerobic Fatty acids Campbell; Fig.40.10 Glucose • Human body regulates the use and storage of glucose. 1 When blood glucose level rises, a gland called the pancreas secretes insulin, a hormone, into the blood. 2 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. STIMULUS: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood Figure 41.3 4 Glucagon promotes the breakdown of glycogen in the liver and the release of glucose into the blood, increasing blood glucose level. STIMULUS: Blood glucose level drops below set point. 3 When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin. Stores of glycogen and fat are used up – so what is left? Undernourished – calorie deficient Overnourished – calorie excess Hypothalamic feeding center Food intake Fat stores Leptin secretion Negative feedback Neuropeptide Y Hypothalamic feeding center Negative feedback Neuropeptide Y X Food intake Fat stores X Leptin secretion Hormones and Appetite Secreted by the stomach wall, ghrelin is one of the signals that triggers feelings of hunger as mealtimes approach. In dieters who lose weight, ghrelin levels increase, which may be one reason it’s so hard to stay on a diet. Produced by adipose (fat) tissue, leptin suppresses appetite as its level increases. When body fat decreases, leptin levels fall, and appetite increases. Ghrelin Insulin Figure The hormone PYY, secreted by the small intestine after meals, acts as an appetite suppressant that counters the appetite 41.5 stimulant ghrelin. Leptin PYY A rise in blood sugar level after a meal stimulates the pancreas to secrete insulin (see Figure 41.3). In addition to its other functions, insulin suppresses appetite by acting on the brain. Malnourished – diet is missing one or more essential nutrients Materials that must be obtained in their preassembled form because animal cells cannot make them from any raw material Osteophagia – bone eating Essential Nutrients Essential amino acids Essential fatty acids Vitamins Minerals In order for protein synthesis to occur in human adults, eight amino acids must be available simultaneously and in the correct relative amounts Important for phospholipid membrane; and principal storage compound Organic molecules in small amounts Inorganic molecules in small amounts Water soluble Fat soluble Food Processing Ingestion Digestion Absorption Elimination Act of eating Process of breaking food down into molecules small enough for the body to absorb Take up small molecules from the digestive compartment Undigested material passes out of the digestive compartment Intracellular Extracellular Food Processing Digestion Process of breaking food down into molecules small enough for the body to absorb Intracellular Extracellular Campbell; Fig.41.10 Food Processing Digestion Process of breaking food down into molecules small enough for the body to absorb Intracellular Gastrovascular cavity Extracellular Complete digestive tract or alimentary canal Campbell; Fig.41.11 Campbell; Fig. 33.4 Campbell; Fig. 33.10 Campbell; Fig. 41.13 Campbell; Fig.41.12a Campbell; Fig.41.12b Highly reliant on digestive system to remain healthy Cannot afford to store heavy materials in body for lengthy period Campbell; Fig.41.12c 1. Mouth – usually relatively simple 2. Esophagus – may be widened at midpoint to form crop (storage area) 3. Proventriculus – glandular stomach which is highly acidic 4.Gizzard – thick muscular walls and sandpaper like surface stomach 5.Small intestine – food digestion and absorption 6. Caecum – bacterial breakdown of cellulose 7. Large intestine 8. Cloaca – final holding area Proctor and Lynch; Manual of Ornithology EVOLUTIONARY ADAPTATIONS OF VERTEBRATE DIGESTIVE SYSTEMS 1. Length of digestive system 2. Accessory structures (such as) a. Crop b. Gizzard c. Liver d. Caeca Campbell; Fig. 41.21 Herbivorous Bird Carnivorous Bird Grain Fruits and Berries Gizzard Substantial Substantial Reduced in size Small intestine Shorter, less complex Longer, more complex Shorter, less complex Caeca Small or absent Well developed Less well developed EVOLUTIONARY ADAPTATIONS OF VERTEBRATE DIGESTIVE SYSTEMS Dentition Many kinds of animals have tooth–like structures, but only vertebrates have true teeth, with an ultrahard layer of ENAMEL on the outside and softer DENTINE on the inside. Campbell; Fig. 41.20 The incisors in blue (cutting plant food) The canines in red (slicing and tearing meat) The molars in green (grinding grass and other plants) http://www.oum.ox.ac.uk/children/animals/nuteeth.htm http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/kinds_of_teeth.html Examples of modified incisors EVOLUTIONARY ADAPTATIONS OF VERTEBRATE DIGESTIVE SYSTEMS X Use of Symbiotic Microorganisms Campbell; Fig. 41.22 Campbell; Fig.41.22 Four compartment stomach 1. Reticulum – form food bolus and initiate regurgitation Reticular epithelium – honeycomb lining Four compartment stomach 1. Reticulum – form food bolus and initiate regurgitation 2. Rumen – digestive and fermentation vat containing anaerobic microbes and site of fatty acid absorption Rumen Interior http://www.borderouge.com/photos/c hai.jpg Four compartment stomach 1. Reticulum – form food bolus and initiate regurgitation 2. Rumen – digestive and fermentation vat, contains anaerobic microbes, site of fatty acid absorption 3. Omasum – lined by muscular folds, reduces particle size, absorbs water (and any leftover fatty acids) Omasum epithelium Four compartment stomach 1. Reticulum – form food bolus and initiate regurgitation 2. Rumen – digestive and fermentation vat, contains anaerobic microbes, site of fatty acid absorption 3. Omasum – lined by muscular folds, reduces particle size, absorbs water (and any leftover fatty acids) 4. Abomasum – true glandular stomach where bacteria and pathogens are killed What do the microbes provide to the ruminants? Symbiotic Microorganisms 1. Digestion of cellulose 2. Provision of organic acids 3. Provision of protein 4. Provision of B vitamins 5. Detoxify compounds What do the ruminants provide to the microbes? Symbiotic Microorganisms 1. Housing with reliable heat 2. Adequate nutrition 3. Garbage removal 4. Neutral environment EVOLUTIONARY ADAPTATIONS OF VERTEBRATE DIGESTIVE SYSTEMS 1. Foregut fermenters a. Cows, sheep, goats 2. Hindgut fermenters a. Horses, rodents, rabbits b. Coprophagy a. Using feces as a nutritional resource b. Food passes through entire digestive tract a second time Campbell; Fig. 41.21