Animal Nutrition

Nutrition: food taken in, food taken apart, food
taken up

Nutrition is essential for


Energy production (ATP): all activities from
molecular to cellular level
Biosynthesis: supply raw materials to build
complex molecules to grow, maintain & reproduce
Animals have diverse diets:

herbivores

carnivores

omnivores

Most animals are opportunistic feeders

Essential nutrients: materials that an
animal’s cells require but cannot synthesize.

4 classes of essential nutrients:




essential amino acids
essential fatty acids
vitamins
minerals

Amino acids: Organic molecule with an amino
group and an acid group

Essential amino acids:


Must be obtained from prefabricated food
8 in humans (infants - 9 – histidine)
Animal products (meat, cheese, eggs) are
complete “proteins”.

Most plants have “incomplete proteins”
Essential amino acids for adults
Methionine
Valine
Threonine
Phenylalanine
Leucine
Corn (maize)
and other grains
Isoleucine
Tryptophan
Lysine
Beans
and other
legumes

Temporary use of muscle protein as a source of
amino acids (penguins).

Essential fatty acids:



Long carbon chain with an acid group
Unsaturated fatty acids (linoleic acid to make membrane
phospholipids)
Seeds, grains vegetables
Saturated
Fatty acid
Unsaturated Fatty acid
Vitamins:
 Organic molecules with diverse functions;
required in the diet in small amounts.
 Water soluble: B-complex, C, Biotin
 Fat soluble: A, D, E, K


Minerals:
Inorganic nutrients required in small amounts
Dietary deficiencies:
 Undernourishment: diet that supplies
insufficient chemical energy
 Malnourishment: long term absence from
diet of one or more essential nutrients

Undernourishment:
diet that supplies
insufficient chemical
energy





Body uses up stored fats
and carbohydrates
Breaks down muscles
Brain will become protein
deficient
Death or irreversible
damage
Places with turmoil in
society (war, drought), or
eating disorders

Malnourishment: long term absence from
diet of one or more essential nutrients



Among herbivores (fragile bones from lack of
phosphorus)
Carnivores switch prey
Disease, deformities, death in humans, especially
children

Four main feeding mechanisms in
animals:




Suspension feeders
Substrate feeders
Fluid feeders
Bulk feeders

Suspension feeders: clams, oysters, whales

Substrate feeders: live in or on the food
source, caterpillars
Caterpillar
Feces

Fluid feeders: suck nutrient-rich fluid from
living host (have specialized organs)

Bulk feeders: Eat large pieces of food.

Four main stages of nutrition:




Ingestion: act of eating
Digestion: food is broken down into small
molecules that can be absorbed; mechanical &
chemical – enzymatic hydrolysis)
Absorption: animal cells take up the break-down
products
Elimination: passing out undigested material
LE 41-12
Small
molecules
Pieces
of food
Mechanical
digestion
Chemical digestion
Nutrient
(enzymatic hydrolysis) molecules
enter body
cells
Undigested
material
Food
INGESTION
DIGESTION
ABSORPTION
ELIMINATION

Intracellular digestion: food is broken
down inside food vacuoles

Extracellular digestion: Breakdown happens
in compartments that are outside of the body;
hydra, earthworm, grasshopper, birds, humans
Mouth
Tentacles
Gastrovascular
Food cavity
Epidermis
Mesoglea
Gastrodermis
Nutritive
muscular
cells
Flagella
Gland cells
Food vacuoles
Mesoglea
Crop Gizzard
Intestine
Esophagus
Pharynx
Anus
Mouth
Typhlosole
Lumen of intestine
Earthworm
Foregut
Midgut
Esophagus
Hindgut
Rectum
Anus
Crop
Mouth
Grasshopper
Gastric ceca
Esophagus
Stomach
Gizzard
Intestine
Mouth
Crop
Anus
Bird

Salivary
glands
Human digestive system
Mouth
Esophagus
Gallbladder
Liver
Pancreas
Stomach
Small
intestines
Large
intestines
Rectum
Anus
A schematic diagram of the
human digestive system

Peristalsis: alternating
waves of contraction
and relaxation in the
smooth muscles lining
the alimentary canal.

Oral cavity:


Mechanical digestion, chewing.
Chemical digestion: Saliva
Carbohydrate digestion
Oral cavity, Polysaccharides Disaccharides
pharynx,
Salivary amylase
esophagus
Smaller polysaccharides, maltose
Protein digestion
Nucleic acid digestion
Fat digestion

Functions of saliva





salivary amylase, hydrolyzes starch
lubrication: mucin (glycoprotein)
preparation of food bolus
buffer
antibacterial function

Swallowing has to be carefully choreographed to
prevent food from entering airway

Stomach:




stores food
continues digestion by churning and mixing with
gastric juices (chyme).
low pH (~2)kills bacteria, HCl secreted by parietal
cells
digests protein – pepsin, chief cells produce
pepsinogen which is activated by HCl.
Esophagus
Cardiac orifice
Stomach
5 µm
Pyloric sphincter
Interior surface of stomach
Small
intestine
Folds of
epithelial
tissue
Epithelium
Pepsinogen
Gastric gland
Pepsin
(active enzyme)
HCl
Pepsinogen and HCl
are secreted into the
lumen of the stomach.
HCl converts
pepsinogen to pepsin.
Pepsin then activates
more pepsinogen,
starting a chain
reaction. Pepsin
begins the chemical
digestion of proteins.
Mucus cells
Chief cells
Parietal cells
Chief cell
Parietal cell




Stomach secretes thick mucus to prevent its
cells from getting corroded by HCl.
Sphincter (ring-like valve) at the junction of
stomach and esophagus prevents backflow.
Backflow causes “heartburn”.
Sphincter between stomach and small
intestine allows food to go out in squirts.
Takes 2 to 6 hrs after a meal for the stomach
to empty.
Figure 22.10
Carbohydrate digestion
Protein digestion
Oral cavity, Polysaccharides Disaccharides
pharynx,
Salivary amylase
esophagus
Smaller polysaccharides, maltose
Stomach
Proteins
Pepsin
Small polypeptides
Nucleic acid digestion
Fat digestion
Bacteria
1 µm
Mucus
layer of
stomach



Small intestine:
very long, small in diameter;
three sections



duodenum
jejunum
ileum
Duodenum:
 Chyme mixes with
digestive juices from



Liver and gall bladder
Pancreas
Intestinal wall



Bulk of digestion happens here
Continues in the jejunum and ileum
Bile salts produced by liver helps in the
digestion of fats
Pancreas
Membrane-bound
enteropeptidase
Inactive
trypsinogen
Other inactive
proteases
Lumen of duodenum
Trypsin
Active
proteases
Carbohydrate digestion
Protein digestion
Nucleic acid digestion
Fat digestion
Oral cavity, Polysaccharides Disaccharides
pharynx,
Salivary amylase
esophagus
Smaller polysaccharides, maltose
Stomach
Proteins
Pepsin
Small polypeptides
Lumen of
small intestine
Polysaccharides
Polypeptides
Pancreatic amylases
Pancreatic trypsin
and chymotrypsin
Maltose and other
disaccharides
DNA, RNA
Pancreatic
nucleases
Nucleotides
Pancreatic carboxypeptidase
Pancreatic lipase
Amino acids
Disaccharidases
Monosaccharides
Bile salts
Fat droplets
Smaller polypeptides
Epithelium
of small
intestine
(brush
border)
Fat globules
Glycerol, fatty
acids, glycerides
Small peptides
Nucleotidases
Dipeptidases, carboxypeptidase, and
aminopeptidase
Nucleosides
Amino acids
Nucleosidases
and phosphatases
Nitrogenous bases,
sugars, phosphates

Absorption in small intestine


Huge surface area – villi (finger like folds)
Microvilli: folds on the surface of the epithelial
cells
Figure 22.15b

Nutrients convert to water-soluble
chylomicron, transported through lacteal,
goes to the lymph system and to the blood
and heart.

Absorbed nutrients also reach the liver
through hepatic portal vein; nutrient
distribution is controlled by the liver,
detoxification.

Large intestine: consists of



Cecum
Ascending, transverse and descending colon
Rectum

In humans cecum is much reduced




appendix – finger-like extension
90% of the water from the alimentary canal is
absorbed here
Feces: undigested food material
Escherichia coli: breaks down some of the
unabsorbed food material

Form fits function:




Dental adaptations
Stomach and intestinal adaptations
Mutaualistic adaptations
Coprophagous habits
Dental adaptations

Incisors
Molars
Canines
Premolars
Carnivore
Herbivore
Omnivore
Stomach and
intestinal
adaptations
Small intestine
Stomach
Small
intestine
Cecum
Colon
(large
intestine)
Carnivore
Herbivore
LE 41-28
Intestine
Rumen
Reticulum
Esophagus
Abomasum
Omasum

Mutaualistic adaptations

Coprophagous habits: rabbits and rodents eat their
feces to extract all the nutrients
STIMULUS:
Blood glucose
level rises
after eating.
Homeostasis:
90 mg glucose/
100 mL blood

Homeostatic
regulation of
cellular fuel
STIMULUS:
Blood glucose
level drops
below set point.

Overnourishment: Consumption of more
food than needed

Obesity – connected to cancer, heart disease
and diabetes

Recent research: ob gene connected to obesity
in mice

Fat and sugar cravings – evolutionary sense?