Transcript Animal Nutrition - BEHS Science home

Animal Nutrition
Chapter 41
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.)
Nutrition
 Nutrition satisfies three needs of animals:
–fuel (chemical energy) for metabolism
–the organic raw materials (carbon
skeletons)
–essential nutrients
substances animals can’t make
themselves from any raw material
–must obtain in food from
environment
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
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
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
Glucose Regulation (Pancreas)
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
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
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
–Can’t make on their own
–Species specific
–Ex: vitamin C not important in all
species, very important in humans
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
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
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
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
Fatty Acids
 Most fatty acids can be synthesized
 There are a few essential fatty acids
(usually unsaturated)
 Deficiencies are rare
Vitamins
 Required in relatively trace
(minimal) amounts
 However, deficiencies can have
drastic effects
 13 vitamins essential to humans
–water-soluble vitamins
–fat-soluble vitamins
Water Soluble Vitamins
Fat Soluble Vitamins
Minerals
 Simple inorganic nutrients
 Usually required in small amounts
 Ex: Ca+2 and PO4-3 required for bones
 Ex: Iron needed for hemoglobin,
cytochrome complex (ETC)
 Na+, K+ and Cl- needed for osmotic
balance and transport
Minerals
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
Suspension Feeders
 sift small food
particles from the
water
 Ex: baleen
whales, clams
Deposit Feeders (e.g., earthworms)
 Eat their way through dirt or
sediments extract partially decayed
organic material consumed along
with the soil or sediments
Substrate Feeders
 Live in or on their
food source
 Ex: Maggots
consuming a
decaying carcass
 Ex: Leaf Miner
(right) burrows
through leaf
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)
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
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
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
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
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)
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
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
Food Vacuole Digestion
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
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
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
Alimentary Canals
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
Human Digestive System
Levels of Organization
 Cells are the basic functional unit
 Cells  Tissues  Organs  Organ
Systems  Organism
Tissues
 Epithelial tissue covers the surface of the
body and lines the inside of organs
 simple epithelium - single layer of cells;
stratified epithelium - multiple tiers of
cells
 The shapes of cells:
cuboidal (like dice)
columnar (like bricks on end)
squamous (flat like floor tiles)
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
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
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
Epiglottis
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
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
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
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
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
 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
Duodenum
Bile
 Produced by the liver
 Stored in the gallbladder
 Aid in the emulsification (digestion)
and absorption of fats
Digestive Enzyme Specificity (location and substrate)
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
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 doesn’t completely digest to
amino acids
 Trypsin is
secreted as
inactive
trypsinogen by
pancreas
 Intestinal
enzymes activate
trypsin
Protein Digestion
Nucleic Acid Digestion
 First, nucleases break down DNA and
RNA into nucleotides
(Pi+sugar+base)
 Other enzymes then break down the
nucleotides into Pi, sugars, and
nitrogenous bases for reassembly into
new nucleotides
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
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
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
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 indigestible
and becomes roughage of feces
 Digestion is a very energetically and
chemically efficient process
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
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
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
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
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
Dentition
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
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
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
Ruminants