Animal Nutrition

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Animal Nutrition

• Chapter 41

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Nutrition

• Intake of food from external environment
• A balanced diet provides fuel for cellular work
  and the materials needed to construct organic
  molecules
• Proper diet needed in order to maintain
  homeostasis (balanced internal environ.)

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Nutrition

• Nutrition satisfies three needs of animals
• fuel (chemical energy) for metabolism
• the organic raw materials (carbon skeletons)
• essential nutrients,
• substances animals cant make themselves from any
  raw material
• must obtain in food from environment

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Energy (ATP)

• Remember, cell resp. releases ATP by oxidizing
  food molecules
• ATP powers basal or resting metabolism, as well
  as activity, and, in endothermic animals,
  temperature regulation

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Biosynthesis and Energy Storage

• More calories than needed to produce ATP, excess
  can be used for biosynthesis
• growth in size, reproduction, or stored in energy
  depots
• In humans, the liver and muscle cells store
  energy as glycogen (polymer of glucose units)
• If glycogen stores are full and caloric intake
  still exceeds caloric needs, excess stored as fat
• Basis for recent low-carb diet trend

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Regulation of Glucose Levels (ie blood sugar)

• High Glucose (High Blood Sugar)
• Pancreas secretes insulin
• promotes glucose storage as glycogen in
  liver/muscles)
• Low Glucose (Low Blood Sugar)
• Pancreas secretes glucagon
• promotes the breakdown of glycogen and release of
  glucose into blood

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Glucose Regulation (Pancreas)
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Undernourishment

• When not receiving enough calories, the body
  breaks its energy stores down
• Body first depends on liver stores, then muscle
  and fat glycogen
• Average adult has enough fat stores for weeks of
  starvation
• Severe malnutrition leads to loss of muscle mass
  and loss of brain proteins
• Brain damage, death, or permanent disability
  possible

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Overnourishment

• Leads to obesity (excess fat stores)
• Leads to serious health issues, especially
  cardiovascular disease and death
• Excess carbs leads to storage as fat molecules
• Hormones are involved in the regulation of fat
  storage

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You are What you Eat

• In addition to needing energy, you must take in
  certain molecules needed as raw materials (mostly
  C-skeletons) for important biomolecules
• essential nutrients
• must obtain from environment
• Cant make on their own
• Species specific
• Ex vitamin C not important in all species, very
  important in humans

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Malnourishment

• Diet lacking in one or more essential nutrients
• Even possible for an overnourished individual to
  be malnourished
• Much more common in humans than undernourishment

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Amino Acids

• Animals require about 20 amino acids for protein
  synthesis
• Can make about half from raw materials (provided
  enough nitrogen)
• Essential Amino Acids ? Must be obtained in
  preassembled form
• Protein deficiency
• Missing one or more amino acids in diet
• Most common form of malnourishment

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Complete/Incomplete Proteins

• Complete Proteins
• Provide all essential amino acids
• Meat, eggs, cheese (animal products)
• Incomplete Proteins
• Lacking one or more essential amino acids
• Corn, rice, etc all lack an essential amino acid
• Staples in 3rd World Countries

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Overcoming Incomplete Proteins

• Eat a complementary mix of veggies that cover the
  essential amino acids
• Eating the right mix of incomplete proteins is as
  effective as eating complete proteins

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Fatty Acids

• Most fatty acids can be synthesized
• There are a few essential fatty acids (usually
  unsaturated)
• Deficiencies are rare

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Vitamins

• Required in relatively trace (minimal) amounts
• However, deficiencies can have drastic effects
• 13 vitamins essential to humans
• water-soluble vitamins
• fat-soluble vitamins

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Water Soluble Vitamins
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Fat Soluble Vitamins
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Minerals

• Simple inorganic nutrients
• Usually required in small amounts
• Ex Ca2 and PO4-3 required for bones
• Ex Iron needed for hemoglobin, cytochrome
  complex (ETC)
• Na, K and Cl- needed for osmotic balance and
  transport

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Minerals
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Types of Nutrition

• Herbivores (gorillas, cows, hares) ? eat mainly
  autotrophs (plants, algae)
• Carnivores (sharks, hawks, spiders, and snakes) ?
  eat other animals
• Omnivores (humans) ? consume animal and plant or
  algal matter

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Suspension Feeders

• sift small food particles from the water
• Ex baleen whales, clams

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Deposit Feeders (ie earthworms)

• Eat their way through dirt or sediments extract
  partially decayed organic material consumed along
  with the soil or sediments

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Substrate Feeders

• Live in or on their food source
• Ex Maggots consuming a decaying carcass
• Ex Leaf Miner (right) burrows through leaf

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Fluid Feeders

• Suck nutrient-rich fluids from a living host
• Often considered parasites
• Ex Mosquitoes and leaches suck blood from
  animals
• Ex Aphids tap the phloem sap of plants
• Ex Hummingbirds and bees are good fluid feeders
  (nectar)

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Bulk Feeders

• Most animals eat relatively large portions of
  food when available
• This is sort of a take it while you can get it
  approach to nutrition b/c food can be scarce

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Ingestion ? Take Food In

• Act of eating
• First stage of food processing
• Food molecules cannot be used as-is and must be
  digested in order for the cells to make use of
  them as nutrients

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Digestion ? Break Food Down

• Why is food digested??
• Polymers in food molecules too large to pass into
  cells
• Macromolecules in food are not exactly what makes
  up the animal eating them
• However, animals all use common monomers to
  assemble macromolecules

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Digestion

• Break food down into small, absorbable molecules
• Polysaccharides and disaccharides are split into
  simple sugars.
• Fats are digested to glycerol and fatty acids.
• Proteins are broken down into amino acids.
• Nucleic acids are cleaved into nucleotides

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Enzymatic Hydrolysis

• Reverse process as dehydration synthesis
• Enzymes are used to cleave polymers into monomers
• Specific enzymes digest the specific classes of
  macromolecules
• Chemical digestion (enzymes) is generally
  preceded by mechanical digestion (chewing,
  gizzard)

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Absorption and Elimination

• Useful nutrient molecules are absorbed and used
  by the animal
• Molecules that have little use in the organism
  are eliminated as waste

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Digestion

• Specialized organs perform the various digestion
  of food molecules
• Keeps organisms from digesting their own cells
• Intracellular Digestion
• Food vacoules break down particles via hydrolytic
  enzymes
• Sole digestion of many protists

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Food Vacuole Digestion
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Extracellular Digestion

• Takes place outside of cells
• Fungi release enzymes into the soil that digest
  their food before it enters them
• Allows smaller single-celled organisms to consume
  larger food molecules than phagocytosis

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Gastrovascular Cavities

• Single opening digestive systems
• Food enters mouth, is digested in GV cavity, and
  undigested material is eliminated back through
  the mouth
• Cnidaria, flatworms

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Alimentary Canals (complete digestive tube)

• Mouth, digestive tube (stomach, gizzard,
  intestines), and anus
• Runs in one direction, food processed differently
  in different compartments
• Mouth ? Pharynx ? Esophagus ? Crop/Gizzard/Stomach
  (species dep.) ?Intestines ? Anus

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Alimentary Canals
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Human Digestion

• 5 to 10 seconds in esophagus
• 2 to 6 hrs in the stomach being partially
  digested
• 5 to 6 hrs in small intestine (final digestion
  and nutrient absorption)
• 12 to 24 hours after consumption, undigested
  material eliminated through large intestine and
  anus

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Human Digestive System
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Levels of Organization

• Cells are the basic functional unit
• Cells ? Tissues ? Organs ? Organ Systems ?
  Organism

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Tissues

• Epithelial tissue covers the surface of the body
  and lines the inside of organs
• A simple epithelium - single layer of cells, and
  stratified epithelium - has multiple tiers of
  cells.
• The shapes of cells
• cuboidal (like dice)columnar (like bricks on
  end)
• squamous (flat like floor tiles)

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Muscles

• Many muscles are involved in digestion
• Some are voluntarily controlled (skeletal muscle)
  and others are involuntarily controlled (smooth
  muscle)
• Skeletal ? Striated, voluntary, found in muscles
  and other voluntarily controlled sphincters
• Smooth ? Not striated, involuntary, peristalsis
• Cardiac ? Found in the heart, involuntary

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Oral Cavity (Mouth)

• Begins physical (chewing) and chemical digestion
  of food
• Salivary amylase breaks down starch
• Enzyme released in response to food presence
• Chewing increases surface area for chemical
  digestion
• Saliva also lubricates food for passage through
  esophagus

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Pharynx

• Between the mouth and the esophagus
• Epiglottis ? Flap of skin that keeps the bolus
  (food ball) from going down the wrong pipe
• When swallowing, the epiglottis covers the
  trachea and diverts food into the esophagus

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Epiglottis
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Esophagus

• Top muscles are voluntary (part of swallowing you
  control)
• Involuntary series of muscle contractions
  (peristalsis) move food from mouth to stomach
  after it passes into esophagus from pharynx

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Stomach

• Chemical and mechanical digestion (involuntary)
  proceed in the stomach
• Elastic walls and folds allow the stomach to
  churn about 2 L of food/liquid at a time
• Secretes gastric juice (pepsin HCl) that
  chemically digests

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Gastric Juice

• HCl provides acidic environment for pepsin and
  kills bacteria ingested with food
• HCl converts pepsinogen (inactive) to pepsin
  (active)
• Pepsin is an enzyme that hydrolyzes proteins
• Chief cells secrete pepsin
• Parietal cells secrete HCl

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Stomach

• Stomach lining replaced by mitosis every three
  days
• Lining of mucus keeps the pepsin from digesting
  the stomach wall
• H. pylori
• Acid-resistant bacteria that causes human ulcers

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Small Intestine

• Food (now chyme) passes through the pyloric
  sphincter into the small intestine
• Small intestine is about 6m (20feet) in length in
  adult humans
• Most of the digestion and absorption occurs in
  the small intestine
• Adapted to maximize absorptive surface area

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Duodenum

• First 25 cm of small intestine
• Chyme mixed with digestive juices from the
  pancreas, liver, gall bladder, and gland cells of
  the intestinal wall
• pH becomes more basic than stomach was due to
  pancreatic secretions

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Bile

• Produced by the liver
• Stored in the gallbladder
• Aid in the emulsification (digestion) and
  absorption of fats

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Digestive Enzyme Specificity (location and
substrate)
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Starch Digestion

• Begins in the mouth with salivary amylase
• Continues in the small intestine with amylase.
• Amylase breaks polysaccharides into disaccharides
  (sucrose and maltose)
• Maltase and sucrase then break them into monomers
  of glucose and/or fructose for use in cellular
  respiration

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Protein Digestion

• Trypsin is the major enzyme that breaks down
  proteins in the duodenum
• Proteins are broken down into their amiono acids
• Other enzymes act upon the polypeptides produced
  by trypsin if trypsin doesnt completely digest
  to amino acids

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Protein Digestion

• Trypsin is secreted as inactive trypsinogen by
  pancreas
• Intestinal enzymes activate trypsin

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Nucleic Acid Digestion

• First, nucleases break down DNA and RNA into
  nucleotides (Pisugarbase)
• Other enzymes then break down the nucleotides
  into Pi, sugars, and nitrogenous bases for
  reassembly into new nucleotides

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Fat Digestion

• Fat does not get digested until the small
  intestine
• Bile released by the gallbladder emulsifies the
  fats
• Emulsification ? Separate fats into tiny droplets
• Lipases then hydrolyzes the fats into fatty acids
  and glycerol

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Small Intestine

• Most of the digestion occurs in the duodenum
• Jujenum and ileum function mainly as absorptive
  surfaces
• Absorption of nutrients and water
• Small intestine has approx. same surface area as
  a tennis court to increase absorption

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Absorption

• Folds and projections increase the SI surface
  area
• Villi and microvilli are projections that
  increase SA
• Lacteals
• Networks of blood vessels (capillaries) that
  absorb nutrients across intestinal wall
• Only 2 layers of cells separate lacteals from
  lumen of intestine

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Absorption

• Depending on the size and charge of the nutrient
  involved, absorption can either be passive or
  active
• People eating a good diet absorb about 85 of the
  organic nutrients they consume
• Cellulose (plant cell walls) is undigestible and
  becomes roughage of feces
• Digestion is a very energetically and chemically
  efficient process

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Hormones and Digestion

• The sight, smell, or taste of food causes the
  brain to send a chemical signal to the digestive
  organs to prepare to digest
• Hormones in the various organs cause the
  secretion of the necessary digestive juices

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The Large Intestine (Colon)

• Major function is reabsorption of water
• b/t SI and LI, 90 of H2O reabsorbed
• Peristalsis moves feces through the colon towards
  the rectum
• Diarrhea ? Too little H2O reabsorbed
• Constipation ? Too much H2O reabsorbed

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Intestinal Bacteria

• E coli is the main bacteria found in the
  intestine
• Most of the bacteria live off of excess nutrients
  and release vitamins for us
• Bacteria are also involved in the regulation of
  water reabsorption
• This is why antibiotics can cause diarrhea

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Feces

• Feces contain the undigested materials being
  eliminated by the organism
• They often contain a lot of cellulose and salts
• They are stored in the rectum and eliminated
  through the anus
• Two sphincters (one voluntary, one not) control
  defecation

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Dentition

• Teeth are adapted to the type of food the
  organisms consume
• For example, horses have large flat teeth for
  grinding grasses while wolves have sharp teeth to
  tear at prey flesh
• Humans show intermediate dentition because we
  have evolved as omnivores

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Dentition
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Length of Digestive System

• Since vegetation has cell walls, herbivores have
  longer alimentary canals to allow for adequate
  nutrient extraction
• Takes longer to extract nutrients from plants

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Symbiosis

• Animals that do not have enzymes to digest
  cellulose form relationships with bacteria that
  do have these enzymes
• Ex Horse
• The bacteria break down the cellulose and the
  simpler sugars are absorbed by the animal

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Ruminants

• Deer, cattle, sheep
• As the animal eats grasses, the grasses pass
  through structures (rumen, reticulum) where
  microorganisms digest cellulose
• After being processed by microorganisms, the food
  passes through to be fully digested and absorbed

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Ruminants