Chapter 50 Animal Nutrition

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Chapter 50Animal Nutrition
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Chapter 50 Animal Nutrition

• Nutrient Requirements
• Adaptations for Feeding
• Digestion
• Structure and Function of the Vertebrate Gut

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Chapter 50 Animal Nutrition

• Control and Regulation of Digestion
• Control and Regulation of Fuel Metabolism
• The Regulation of Food Intake
• Toxic Compounds in Food

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Nutrient Requirements

• Animals are heterotrophs that derive their energy
  and structural building blocks from food,
  therefore ultimately from autotrophs.
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Nutrient Requirements

• Carbohydrates, fats, and proteins supply animals
  with metabolic energy.
• A measure of the energy content of food is the
  calorie.
• Excess caloric intake is stored as glycogen and
  fat.
• Review Figure 50.2
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50.2
figure 50-02.jpg

• Figure 50.2

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Nutrient Requirements

• An animal with insufficient caloric intake is
  undernourished and must metabolize its stored
  glycogen, fat, and finally its own protein.
• Overnutrition in humans can be a serious health
  hazard.
• Review Figure 50.3
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50.3
figure 50-03.jpg

• Figure 50.3

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Nutrient Requirements

• For many animals, food provides essential carbon
  skeletons they cannot synthesize themselves.
• Review Figure 50.4
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50.4
figure 50-04.jpg

• Figure 50.4

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Nutrient Requirements

• Humans require eight essential amino acids.
• All are available in milk, eggs, or meat, but not
  in all vegetables.
• Thus, vegetarians must eat a mix of foods.
• Review Figure 50.5
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50.5
figure 50-05.jpg

• Figure 50.5

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Nutrient Requirements

• Different animals need mineral elements in
  different amounts.
• Macronutrients are needed in large amounts.
• Micronutrients are needed in small amounts.
• Review Table 50.1
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50.1
table 50-01a.jpg

• Table 50.1 Part 1

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table 50-01b.jpg
50.1
Table 50.1 Part 2
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Nutrient Requirements

• Vitamins are organic molecules that must be
  obtained in food.
• Review Table 50.2
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50.2
table 50-02a.jpg

• Table 50.2 Part 1

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50.2
table 50-02b.jpg
Table 50.2 Part 2
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Nutrient Requirements

• Malnutrition results when any essential nutrient
  is lacking from the diet.
• Lack of any essential nutrient causes a
  deficiency disease.
• Review Table 50.2
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50.2
table 50-02a.jpg

• Table 50.2 Part 1

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50.2
table 50-02b.jpg
Table 50.2 Part 2
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Adaptations for Feeding

• Animals can be characterized by how they acquire
  nutrition
• Saprotrophs and detritivores depend on dead
  organic matter
• Filter feeders strain the environment for food
• Herbivores eat plants
• Carnivores eat animals.
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Adaptations for Feeding

• Behavioral and anatomical adaptations reflect
  feeding types.
• In vertebrates, teeth have evolved to match diet.
  
• Review Figure 50.9
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50.9
figure 50-09a.jpg

• Figure 50.9 Part 1

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50.9
figure 50-09b.jpg
Figure 50.9 Part 2
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Digestion

• Digestion involves the breakdown of complex food
  molecules into monomers that can be absorbed and
  utilized by cells.
• In most animals, digestion is extracellular,
  external to the body, occurring in a tubular gut
  with regions specialized for different digestive
  functions.
• Review Figure 50.10
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50.10
figure 50-10.jpg

• Figure 50.10

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Digestion

• Absorptive areas of the gut are characterized by
  a large surface area.
• Review Figure 50.11
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50.11
figure 50-11a.jpg

• Figure 50.11 Part 1

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50.11
figure 50-11b.jpg

• Figure 50.11 Part 2

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Digestion

• Hydrolytic enzymes break down proteins,
  carbohydrates, and fats into their monomeric
  units.
• To prevent the organism itself from being
  digested, these are released as inactive
  zymogens, only activated when secreted into the
  gut.
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Structure and Function of the Vertebrate Gut

• Cells and tissues of the vertebrate gut are
  organized in the same way throughout its length.
• The innermost tissue layer, the mucosa, is the
  secretory and digestive surface.
• The submucosa contains secretory cells and
  glands, blood and lymph vessels, and nerves.
• External to the submucosa are two smooth muscle
  layers that move food through the gut.
• Between these is a nerve network that controls
  gut movements. Review Figure 50.13
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50.13
figure 50-13.jpg

• Figure 50.13

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Structure and Function of the Vertebrate Gut

• The swallowing reflex pushes food into the
  esophagus.
• Waves of smooth muscle contraction and relaxation
  (peristalsis) move food from the beginning of the
  esophagus through the length of the gut.
• Sphincters block the gut at certain locations,
  but relax as a wave of peristalsis approaches.
• Review Figure 50.14
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50.14
figure 50-14a.jpg

• Figure 50.14 Part 1

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50.14
figure 50-14b.jpg

• Figure 50.14 Part 2

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Structure and Function of the Vertebrate Gut

• Enzymatic digestion begins in the mouth, where
  amylase is secreted with saliva.
• Protein digestion begins in the stomach with
  pepsin and HCl secreted by the stomach mucosa.
• The mucosa also secretes mucus, to protect gut
  tissues.
• Review Figure 50.15
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50.15
figure 50-15.jpg

• Figure 50.15 Part 1

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50.15
figure 50-15b.jpg

• Figure 50.15 Part 2

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Structure and Function of the Vertebrate Gut

• In the the duodenum, pancreatic enzymes carry out
  most of digestion.
• Bile from liver and gallbladder assists in
  digestion of fats, breaking them into micelles.
• Bicarbonate ions from the pancreas neutralize the
  pH of the chyme entering from the stomach to
  produce an environment conducive to pancreatic
  enzyme action.
• Review Figure 50.16, Table 50.3
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50.16
figure 50-16.jpg

• Figure 50.16

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50.3
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• Table 50.3

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Structure and Function of the Vertebrate Gut

• Final enzymatic cleavage of peptides and
  disaccharides occurs on the cell surfaces of the
  intestinal mucosa.
• Amino acids, monosaccharides, and many inorganic
  ions are absorbed by the microvilli of the
  mucosal cells.
• Often specific carrier proteins in the membranes
  of these cells transport nutrients into the
  cells.
• Sodium cotransport is a common mechanism for
  actively absorbing nutrient molecules and ions.
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Structure and Function of the Vertebrate Gut

• Fats are absorbed mostly as monoglycerides and
  fatty acids, the product of lipase action on
  triglycerides in food.
• These products pass through mucosal cell
  membranes and are resynthesized into
  triglycerides within the cells.
• The triglycerides are combined with cholesterol
  and coated with protein to form chylomicrons,
  which pass out of mucosal cells into lymphatic
  vessels in the submucosa.
• Review Figure 50.17
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50.17
figure 50-17.jpg

• Figure 50.17

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Structure and Function of the Vertebrate Gut

• Water and ions are absorbed in the large
  intestine so that waste matter is consolidated
  into feces.
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Structure and Function of the Vertebrate Gut

• In herbivores such as rabbits and ruminants, some
  compartments of the gut have populations of
  microorganisms that aid in digesting molecules
  otherwise indigestible.
• Review Figure 50.18
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50.18
figure 50-18.jpg

• Figure 50.18

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Control and Regulation of Digestion

• Digestion processes are coordinated and
  controlled by neural and hormonal mechanisms.
• Salivation and swallowing are autonomic reflexes.
  
• Stomach and small intestine actions are largely
  controlled by the hormones gastrin, secretin, and
  cholecystokinin.
• Review Figure 50.19
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50.19
figure 50-19.jpg

• Figure 50.19

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Control and Regulation of Fuel Metabolism

• The liver interconverts fuel molecules and plays
  a central role in directing their traffic.
• When food is being absorbed from the gut, the
  liver takes up and stores fats and carbohydrates,
  converting monosaccharides to glycogen or fat.
• The liver also takes up amino acids and uses them
  to produce blood plasma proteins.
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Control and Regulation of Fuel Metabolism

• Fat and cholesterol are shipped out of the liver
  as low-density lipoproteins.
• High-density lipoproteins act as acceptors of
  cholesterol and are believed to bring fat and
  cholesterol back to the liver.
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Control and Regulation of Fuel Metabolism

• Fuel metabolism during the absorptive period is
  controlled largely by insulin, which promotes
  glucose uptake and utilization by most cells of
  the body, as well as fat synthesis in adipose
  tissue.
• During the postabsorptive period, lack of insulin
  blocks the uptake and utilization of glucose by
  most body cells except neurons.
• If blood glucose levels fall, glucagon is
  secreted, stimulating the liver to break down
  glycogen to release glucose.
• Review Figures 50.20, 50.21
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50.20
figure 50-20.jpg

• Figure 50.20

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50.21
figure 50-21a.jpg

• Figure 50.21 Part 1

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50.21
figure 50-21b.jpg

• Figure 50.21 Part 2

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The Regulation of Food Intake

• Food intake is governed by sensations of hunger
  and satiety determined by brain mechanisms.
• When one hypothalamic region is damaged, rats eat
  more when another region is damaged, they eat
  less.
• A number of molecules provide feedback
  information to these brain areas.
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The Regulation of Food Intake

• Leptin is a hormone produced by fat cells that
  inhibits food intake.
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Toxic Compounds in Food

• Even natural plant and animal foods can contain
  toxic compounds.
• Human activities such as pesticide use and
  pollution of environment have made the problem of
  toxins in food worse.
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Toxic Compounds in Food

• An organism can accumulate toxic compounds in its
  body, especially if those compounds are
  lipid-soluble or take the structural place of a
  natural molecule.
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Toxic Compounds in Food

• Toxins such as PCBs and DDT that accumulate in
  the bodies of prey are transferred to and further
  concentrated in the bodies of their predators.
• This bioaccumulation produces high concentrations
  of toxins in animals high up the food chain.
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