chapter 50 animal nutrition

Chapter 50: Animal Nutrition

Chapter 50Animal Nutrition



Nutrient RequirementsNutrient Requirements

Adaptations for FeedingAdaptations for Feeding

DigestionDigestion

Structure and Function of the VertebrateStructure and Function of the Vertebrate

Gut Gut



Control and Regulation of DigestionControl and Regulation of Digestion

Control and Regulation of Fuel Control and Regulation of Fuel

MetabolismMetabolism

The Regulation of Food IntakeThe Regulation of Food Intake

Toxic Compounds in FoodToxic Compounds in Food


Nutrient Requirements

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

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• Carbohydrates, fats, and proteins Carbohydrates, fats, and proteins supply animals with metabolic energy. supply animals with metabolic energy.

• A measure of the energy content of A measure of the energy content of food is the calorie. food is the calorie.

• Excess caloric intake is stored as Excess caloric intake is stored as glycogen and fat. glycogen and fat.

Review Figure 50.2Review Figure 50.2

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50.2

Figure 50.2Figure 50.2

figure 50-02.jpgfigure 50-02.jpg



• An animal with insufficient caloric An animal with insufficient caloric intake is undernourished and must intake is undernourished and must metabolize its stored glycogen, fat, metabolize its stored glycogen, fat, and finally its own protein. and finally its own protein.

• Overnutrition in humans can be a Overnutrition in humans can be a serious health hazard. serious health hazard.


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• For many animals, food provides For many animals, food provides essential carbon skeletons they cannot essential carbon skeletons they cannot synthesize themselves. synthesize themselves.


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• Humans require eight essential amino Humans require eight essential amino acids. acids.

• All are available in milk, eggs, or meat, All are available in milk, eggs, or meat, but not in all vegetables. but not in all vegetables.

• Thus, vegetarians must eat a mix of Thus, vegetarians must eat a mix of foods. foods.


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• Different animals need mineral Different animals need mineral elements in different amounts. elements in different amounts.

• Macronutrients are needed in large Macronutrients are needed in large amounts. amounts.

• Micronutrients are needed in small Micronutrients are needed in small amounts. amounts.

Review Table 50.1Review Table 50.1

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50.1

Table 50.1 – Part 1Table 50.1 – Part 1

table 50-01a.jpgtable 50-01a.jpg


50.1


table 50-01b.jpgtable 50-01b.jpg



• Vitamins are organic molecules that Vitamins are organic molecules that must be obtained in food. must be obtained in food.


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• Malnutrition results when any essential Malnutrition results when any essential nutrient is lacking from the diet. nutrient is lacking from the diet.

• Lack of any essential nutrient causes a Lack of any essential nutrient causes a deficiency disease. deficiency disease.


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Adaptations for Feeding

• Animals can be characterized by how Animals can be characterized by how they acquire nutritionthey acquire nutrition

• Saprotrophs and detritivores depend Saprotrophs and detritivores depend on dead organic matteron dead organic matter

• Filter feeders strain the environment Filter feeders strain the environment for foodfor food

• Herbivores eat plantsHerbivores eat plants• Carnivores eat animals.Carnivores eat animals.

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Adaptations for Feeding

• Behavioral and anatomical adaptations Behavioral and anatomical adaptations reflect feeding types. reflect feeding types.

• In vertebrates, teeth have evolved to In vertebrates, teeth have evolved to match diet. match diet.


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50.9

Figure 50.9 – Part 1Figure 50.9 – Part 1

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figure 50-09b.jpgfigure 50-09b.jpg

50.9


Digestion

• Digestion involves the breakdown of Digestion involves the breakdown of complex food molecules into monomers complex food molecules into monomers that can be absorbed and utilized by cells. that can be absorbed and utilized by cells.

• In most animals, digestion is extracellular, In most animals, digestion is extracellular, external to the body, occurring in a external to the body, occurring in a tubular gut with regions specialized for tubular gut with regions specialized for different digestive functions. different digestive functions.


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Digestion

• Absorptive areas of the gut are Absorptive areas of the gut are characterized by a large surface area. characterized by a large surface area.


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Digestion

• Hydrolytic enzymes break down Hydrolytic enzymes break down proteins, carbohydrates, and fats into proteins, carbohydrates, and fats into their monomeric units. their monomeric units.

• To prevent the organism itself from To prevent the organism itself from being digested, these are released as being digested, these are released as inactive zymogens, only activated inactive zymogens, only activated when secreted into the gut.when secreted into the gut.

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Structure and Function of the Vertebrate Gut• Cells and tissues of the vertebrate gut are Cells and tissues of the vertebrate gut are

organized in the same way throughout its organized in the same way throughout its length. length.

• The innermost tissue layer, the mucosa, is The innermost tissue layer, the mucosa, is the secretory and digestive surface. the secretory and digestive surface.

• The submucosa contains secretory cells and The submucosa contains secretory cells and glands, blood and lymph vessels, and nerves. glands, blood and lymph vessels, and nerves.

• External to the submucosa are two smooth External to the submucosa are two smooth muscle layers that move food through the muscle layers that move food through the gut. gut.

• Between these is a nerve network that Between these is a nerve network that controls gut movements. Review Figure 50.13controls gut movements. Review Figure 50.13

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Structure and Function of the Vertebrate Gut• The swallowing reflex pushes food into The swallowing reflex pushes food into

the esophagus. the esophagus. • Waves of smooth muscle contraction Waves of smooth muscle contraction

and relaxation (peristalsis) move food and relaxation (peristalsis) move food from the beginning of the esophagus from the beginning of the esophagus through the length of the gut. through the length of the gut.

• Sphincters block the gut at certain Sphincters block the gut at certain locations, but relax as a wave of locations, but relax as a wave of peristalsis approaches. peristalsis approaches.



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Structure and Function of the Vertebrate Gut• Enzymatic digestion begins in the Enzymatic digestion begins in the

mouth, where amylase is secreted with mouth, where amylase is secreted with saliva. saliva.

• Protein digestion begins in the Protein digestion begins in the stomach with pepsin and HCl secreted stomach with pepsin and HCl secreted by the stomach mucosa. by the stomach mucosa.

• The mucosa also secretes mucus, to The mucosa also secretes mucus, to protect gut tissues. protect gut tissues.


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Structure and Function of the Vertebrate Gut• In the the duodenum, pancreatic In the the duodenum, pancreatic

enzymes carry out most of digestion. enzymes carry out most of digestion. • Bile from liver and gallbladder assists Bile from liver and gallbladder assists

in digestion of fats, breaking them into in digestion of fats, breaking them into micelles. micelles.

• Bicarbonate ions from the pancreas Bicarbonate ions from the pancreas neutralize the pH of the chyme neutralize the pH of the chyme entering from the stomach to produce entering from the stomach to produce an environment conducive to an environment conducive to pancreatic enzyme action. pancreatic enzyme action.

Review Figure 50.16, Table 50.3Review Figure 50.16, Table 50.34040


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50.3

Table 50.3Table 50.3

table 50-3.jpgtable 50-3.jpg


Structure and Function of the Vertebrate Gut• Final enzymatic cleavage of peptides Final enzymatic cleavage of peptides

and disaccharides occurs on the cell and disaccharides occurs on the cell surfaces of the intestinal mucosa. surfaces of the intestinal mucosa.

• Amino acids, monosaccharides, and Amino acids, monosaccharides, and many inorganic ions are absorbed by many inorganic ions are absorbed by the microvilli of the mucosal cells. the microvilli of the mucosal cells.

• Often specific carrier proteins in the Often specific carrier proteins in the membranes of these cells transport membranes of these cells transport nutrients into the cells. nutrients into the cells.

• Sodium cotransport is a common Sodium cotransport is a common mechanism for actively absorbing mechanism for actively absorbing nutrient molecules and ions.nutrient molecules and ions.

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Structure and Function of the Vertebrate Gut• Fats are absorbed mostly as monoglycerides Fats are absorbed mostly as monoglycerides

and fatty acids, the product of lipase action and fatty acids, the product of lipase action on triglycerides in food. on triglycerides in food.

• These products pass through mucosal cell These products pass through mucosal cell membranes and are resynthesized into membranes and are resynthesized into triglycerides within the cells. triglycerides within the cells.

• The triglycerides are combined with The triglycerides are combined with cholesterol and coated with protein to form cholesterol and coated with protein to form chylomicrons, which pass out of mucosal chylomicrons, which pass out of mucosal cells into lymphatic vessels in the cells into lymphatic vessels in the submucosa. submucosa.


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Structure and Function of the Vertebrate Gut

• Water and ions are absorbed in the Water and ions are absorbed in the large intestine so that waste matter is large intestine so that waste matter is consolidated into feces.consolidated into feces.

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Structure and Function of the Vertebrate Gut

• In herbivores such as rabbits and In herbivores such as rabbits and ruminants, some compartments of the ruminants, some compartments of the gut have populations of gut have populations of microorganisms that aid in digesting microorganisms that aid in digesting molecules otherwise indigestible. molecules otherwise indigestible.


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Control and Regulation of Digestion• Digestion processes are coordinated Digestion processes are coordinated

and controlled by neural and hormonal and controlled by neural and hormonal mechanisms. mechanisms.

• Salivation and swallowing are Salivation and swallowing are autonomic reflexes. autonomic reflexes.

• Stomach and small intestine actions Stomach and small intestine actions are largely controlled by the hormones are largely controlled by the hormones gastrin, secretin, and cholecystokinin. gastrin, secretin, and cholecystokinin.


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Control and Regulation of Fuel Metabolism• The liver interconverts fuel molecules The liver interconverts fuel molecules

and plays a central role in directing and plays a central role in directing their traffic. their traffic.

• When food is being absorbed from the When food is being absorbed from the gut, the liver takes up and stores fats gut, the liver takes up and stores fats and carbohydrates, converting and carbohydrates, converting monosaccharides to glycogen or fat. monosaccharides to glycogen or fat.

• The liver also takes up amino acids The liver also takes up amino acids and uses them to produce blood and uses them to produce blood plasma proteins.plasma proteins.

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Control and Regulation of Fuel Metabolism

• Fat and cholesterol are shipped out of Fat and cholesterol are shipped out of the liver as low-density lipoproteins. the liver as low-density lipoproteins.

• High-density lipoproteins act as High-density lipoproteins act as acceptors of cholesterol and are acceptors of cholesterol and are believed to bring fat and cholesterol believed to bring fat and cholesterol back to the liver.back to the liver.

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Control and Regulation of Fuel Metabolism• Fuel metabolism during the absorptive period Fuel metabolism during the absorptive period

is controlled largely by insulin, which promotes is controlled largely by insulin, which promotes glucose uptake and utilization by most cells of glucose uptake and utilization by most cells of the body, as well as fat synthesis in adipose the body, as well as fat synthesis in adipose tissue. tissue.

• During the postabsorptive period, lack of During the postabsorptive period, lack of insulin blocks the uptake and utilization of insulin blocks the uptake and utilization of glucose by most body cells except neurons. glucose by most body cells except neurons.

• If blood glucose levels fall, glucagon is If blood glucose levels fall, glucagon is secreted, stimulating the liver to break down secreted, stimulating the liver to break down glycogen to release glucose. glycogen to release glucose.

• Review Figures 50.20, 50.21Review Figures 50.20, 50.21

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The Regulation of Food Intake• Food intake is governed by sensations Food intake is governed by sensations

of hunger and satiety determined by of hunger and satiety determined by brain mechanisms. brain mechanisms.

• When one hypothalamic region is When one hypothalamic region is damaged, rats eat more; when another damaged, rats eat more; when another region is damaged, they eat less. region is damaged, they eat less.

• A number of molecules provide A number of molecules provide feedback information to these brain feedback information to these brain areas.areas.

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The Regulation of Food Intake

• Leptin is a hormone produced by fat Leptin is a hormone produced by fat cells that inhibits food intake.cells that inhibits food intake.

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Toxic Compounds in Food

• Even natural plant and animal foods Even natural plant and animal foods can contain toxic compounds. can contain toxic compounds.

• Human activities such as pesticide use Human activities such as pesticide use and pollution of environment have and pollution of environment have made the problem of toxins in food made the problem of toxins in food worse.worse.

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

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• Toxins such as PCBs and DDT that Toxins such as PCBs and DDT that accumulate in the bodies of prey are accumulate in the bodies of prey are transferred to and further transferred to and further concentrated in the bodies of their concentrated in the bodies of their predators. predators.

• This bioaccumulation produces high This bioaccumulation produces high concentrations of toxins in animals concentrations of toxins in animals high up the food chain.high up the food chain.

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chapter 50 animal nutrition

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