Chapter 41
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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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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)

  • 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.


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

  • 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

  • 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

  • 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

    • 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

    • 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.


    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 (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.


    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

    • 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


    • 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

    • 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.


    • 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

    • 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

    • 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

    • 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 (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


    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

    • 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

    • 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)


    • Thanks for watching!!!


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