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Chapter 41. Animal Nutrition. Jesse Couch Haley McKay. 41.1 Homeostatic Mechanisms manage an animal’s energy budget. Herbivores =eat mainly autotrophs (cattle, hares, snails) Carnivores = eat other animals (hawks, spiders, sharks)

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Animal Nutrition

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Animal nutrition

Chapter 41

Animal Nutrition

Jesse Couch

Haley McKay


41 1 homeostatic mechanisms manage an animal s energy budget

41.1 Homeostatic Mechanisms manage an animal’s energy budget


Animal nutrition

  • Herbivores=eat mainly autotrophs (cattle, hares, snails)

  • Carnivores= eat other animals (hawks, spiders, sharks)

  • Omnivores= eat animals as well as plants or algal matter (humans, raccoons, bears)

  • A diet must satisfy 3 nutritional needs: fuel for cell work, the organic raw materials used in biosynthesis, and essential nutrients such as vitamins.


Animal nutrition

Four Main Feeding Mechanisms of Animals

  • Suspension feeders: sift small food particles from the water (whales)

  • Substrate feeders: live in or one their food source (caterpillars)

  • Fluid feeders: suck nutrient rich fluid from a living host (ticks)

  • Bulk feeders: eat relatively large pieces of food (python)


Glucose regulation

Glucose Regulation

  • If an animal isn’t growing or reproducing the body stores surplus energy in depots (in the form of glycogen in humans)

  • Caloric intake> caloric expenditure= calories stored as fat.

  • Caloric intake< caloric expenditure= fuel taken out of deposits and oxidized.


Caloric imbalance

Caloric Imbalance

  • Undernourishment=occurs if the diet of the animal is chronically deficient in calories.

    - The stores of glycogen are used up and the body starts to break down proteins, muscles decrease in size, brain become protein-deficient.

    - Can cause death or irreversible side-effects

  • Over nourishment=excessive food intake (obesity)

    - Body hoards fat instead of using it for energy expenditure


Obesity as a human health problem

Obesity as a human health problem

  • 15% of children and adolescents in the U.S. are overweight

  • Being overweight contributes to:

    • Diabetes

    • cancer of colon and breast

    • cardiovascular diseases that can lead to heart attacks and strokes.

  • Obesity can be inherited through the coding of genes that produce weight-regulating hormones.

  • Leptin produced by adipose (fat) is one of the feedback mechanisms that keep most people from becoming obese in spite of excess food.


  • Hormone action on satiety center

    Hormone Action on Satiety Center

    • Hormones regulate long-term and short-term appetite by affecting a satiety “center” in the brain

      • Ghrelin: signal that triggers feelings of hunger as mealtimes approach

      • Insulin: secreted from pancreas when after meals when there is an increased blood sugar level

      • Hormone PYY: secreted by small intestine after meals, suppresses appetite

      • Leptin: produced by fat tissue, suppresses appetite as its level increases.


    Obesity and evolution

    Obesity and evolution

    • Fat hoarding may have been an evolutionary advantage in the past

      • humans used to be hunter-gatherers and the humans who had functions that induced them to devour rich, fatty foods when they had the chance

  • Individuals with genes that promoted storage of high-energy molecules during feasts would have out-lived thinner friends during famine.


  • 41 2 an animal s diet must supply carbon skeletons and essential nutrients

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


    Essential nutrients

    Essential nutrients

    • . essential nutrients: cannot be made in cells; come in preassembled forms

    • malnourished: missing essential nutrients

    • Essential Amino Acids

    • must be obtained from food to make full proteins and avoid protein deficiency

    • animal proteins are complete; plant proteins are deficient in some amino acids

    • Essential Fatty Acids

    • particular unsaturated fatty acids; rare deficiencies


    Vitamins and minerals

    Vitamins and Minerals

    • Vitamins (see Table 41.1)

    • 13 organic molecules required in much less quantity than amino and fatty acids

    • water-soluble: B complex; coenzymes in metabolic processes

    • fat-soluble: A, D, E, and K; variety of functions

    • excess vitamins are either excreted through urine or kept in body fat (toxic)

    • Minerals (see Table 41.2)

    • inorganic and required in small amounts


    41 3 the main stages of food processing are ingestion digestion absorption and elimination

    41.3 The main stages of food processing are ingestion, digestion, absorption, and elimination.


    First two stages

    First two stages

    • Ingestion: eating; first stage

      • animals can’t use macromolecules in their food directly since 1) they are too large over membranes; 2) they are not identical to what make up animal bodies

  • Digestion: breaking down food into smaller molecules (monomers)

    • enzymatic hydrolysis: breaks monomers apart by addition of water


  • Third and fourth stages

    Third and fourth stages

    • Absorption: cells take up monomers from digestive compartment

    • Elimination: undigested material exits digestive compartment

    • intracellular digestion: within the cell after pino- or phagocytosis

    • extracellular digestion: within continuous compartments

    • simple animals have gastrovascularcavity: sac with one opening

    • alimentary canal (complete digestive tract): mouth to anus (Figure 41.14)


    41 4 each organ of the mammalian digestive system has specialized food processing functions

    41.4 Each organ of the mammalian digestive system has specialized food-processing functions


    Animal nutrition

    • Peristalsis= rhythmic waves of contraction by smooth muscles in the wall of the canal which pushes food along the tract.

    • Sphincter=the muscular layer of ring-like valves which close off the tube like drawstrings, regulating the passage of materials between chambers of the canal.

      • Pancreas, liver, gallbladder are salivary glands which store digestive juices.


    The oral cavity pharynx and esophagus

    The Oral Cavity, Pharynx, and Esophagus

    • Mouth chews food into smaller pieces and increases surface area

    • Presence of food in oral cavity triggers reflex to secrete saliva through ducts.

    • Salivary amylase= an enzyme that hydrolyzes starch and glycogen and produces smaller polysaccharides and the disaccharide maltose.


    Animal nutrition

    • Bolus= food ball formed by tongue when chewing food, then it is pushed into the pharynx

    • Pharynx= a junction that opens to both the esophagus and windpipe

      • When swallow, windpipe’s opening, the glottis, is blocked by epiglottis so bolus does not go down the windpipe

    • Esophagus= a channel that conducts food from the pharynx down to the stomach by peristalsis


    The stomach

    The Stomach

    • Stomach= an organ of the digestive system that stores food and preforms first steps of digestion

      • Secretes gastric juice=digestive fluid and mixes it with the food through a churning action of smooth muscles in stomach wall

      • Gastric juice has a pH of 2 which is used in stomach to kill bacteria, break up cells in meat and plant material, and hydrolyze proteins through use of pepsin

      • Pepsin doesn’t destroy stomach cells b/c it is secreted in inactive from (pepsinogen) which is activated by the secretion of hydrochloric acid by parietal cells in gastric pits


    The stomach continued

    The Stomach Continued

    • Mucus also protects stomach from self-digestion

    • About every 20 seconds, stomach contents are mixed (hunger pangs=empty stomach turning)

      • creates a nutrient broth (acid chyme) from the recently swallowed meal.

  • Opening from esophagus to stomach (cardiac orifice) normally dilates only when bolus arrives

  • Pyloric sphincter= muscular ring that regulates passage of chyme from stomach to intestine


  • Small intestine

    Small intestine

    • duodenum: first section; acid chyme from stomach mixes with juices from pancreas, bile from the liver and gall bladder and gland cells of intestinal wall

    • absorption of nutrients occurs mostly in small intestine

      • increased by microvillar surface on villi: penetrated by capillaries and lacteal: lymphatic vessel

  • nutrients cross only two layers of epithelial cells from lumen to bloodstream through active or passive transport

  • fats are mixed with cholesterol and coated with proteins to form chylomicrons that enter lacteals


  • Large intestine

    Large intestine

    • Large Intestine (Colon): connected to small intestine at T-shaped junction w/ sphincter controlled movement

    • cecum: one arm of T with appendix

    • recovers water in alimentary canal

    • feces is moved along organ at different speeds; normal speed is slow

    • rectum: end of colon where waste is stored until elimination (contractions of colon)


    V 41 5 evolutionary adaptations of vertebrate digestive systems are often associated with diet

    V.41.5 Evolutionary adaptations of vertebrate digestive systems are often associated with diet


    Some dental adaptations

    Some dental adaptations

    • Different mammals have different teeth for processing certain foods (Figure 41.26 pg. 863)

    • Non-mammalian vertebrate (lizards) usually have less specialized dentition with poisonous snakes as the exception (have specialized fangs with poison)


    Stomach and intestinal adaptations

    Stomach and Intestinal Adaptations

    • Large expandable stomachs are common in carnivores

    • Herbivores and omnivores have longer alimentary canals (digestive tract) b/c vegetation is harder to digest b/c of cell walls


    Symbiotic adaptations

    Symbiotic Adaptations

    • Animals do not produce enzymes that can digest cellulose but their stomach houses microorganisms that do have these enzymes

    • Ruminants= an animal (cow, sheep, deer) with an elaborate, multi-compartmentalized stomach specialized for a herbivorous diet. (figure 41.28 pg.864)


    Animal nutrition

    • Thanks for watching!!!


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