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ANIMAL NUTRITION
CHAPTER 41
Figure 41.0 Animals eating: foal, bear, and stork
Figure 41.5 Storing protein for growth by increasing muscle mass. Proteins
are used for molting (growing new feathers).
Figure 41.2 A ravenous rodent. The obese rat has a defective gene which
normally produces an appetite-regulating protein.
DIETARY CATEGORIES
• Herbivores – eat mainly
autotrophs
• Carnivores – eat mainly
animals
• Omnivores – eat animals,
plants,and/or algae
FEEDING MECHANISMS
• Suspension-feeders – sift
small food particles from water
–clams, oysters, baleen whales
Figure 41.6 Suspension-feeding: a baleen whale
• Substrate-feeders – live in or
on their food source, eating
their way through the food
–Leaf miners (tunnel through
leaves)
–Earthworms (more specifically
deposit feeders)
Figure 41.7 Substrate-feeding: a leaf miner
• Fluid-feeders – sucking
nutrients from living hosts
–Mosquitoes, leeches, aphids
Figure 41.8 Fluid-feeding: a mosquito
• Bulk-feeders – eat relatively
large pieces of food
–Most animals
Figure 41.9 Bulk-feeding: a python
FOUR MAIN STAGES OF
FOOD PROCESSING
• Ingestion
• Digestion
–Enzymatic hydrolysis
• Absorption
• Elimination
INTRACELLULAR DIGESTION
• Food vacuoles fuse with
lysosomes that have hydrolytic
enzymes to digest food
–Sponges (entirely intracellular
digestion)
–Paramecium – oral groove
leads to making food vacuole
Figure 41.10 Intracellular digestion in Paramecium
Figure 41.11 Extracellular digestion in a gastrovascular cavity
EXTRACELLULAR DIGESTION
• Breakdown food outside of cells
in gastrovascular cavities
• Some have single opening
(Incomplete digestive tract)
–Cnidarians and flatworms
• Two openings (Complete
digestive tract or alimentary
canal) – tube with mouth and
anus
–Most animals
–Mouth, pharynx, esophagus,
(crop, gizzard), stomach,
intestine, and anus
Figure 41.12 Alimentary canals
MAMMALIAN DIGESTIVE
SYSTEM
• Peristalsis – contraction of
smooth muscles in wall of canal
• Sphincters – ring-like valves
• Salivary glands, pancreas, liver,
gall bladder
Figure 41.13 The human digestive system
HUMAN DIGESTIVE SYSTEM
• Oral Cavity
–Mucin (glycoprotein) –
protects soft lining
–Salivary amylase –
hydrolyzes starch
–Bolus- food ball that is
swallowed
• The Pharynx
–Epiglottis (cartilaginous flap)
–Esophageal sphincter
contracts, epiglottis up
–Esophageal sphincter relaxed,
epiglottis covers trachea, food
moves into esophagus
Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal
peristalsis
Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal
peristalsis
Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal
peristalsis
• Stomach
–Secretes gastric juice (high
amounts of HCl)
–pH is approximately 2
–Pepsin (in gastric juice)
hydrolyzes proteins
•Chief cells secrete inactive
pepsinogen
•Parietal cells secrete HCl that
converts pepsinogen into
pepsin
–Stomach lining replaced every 3
days
–Ulcers normally caused by acidtolerant bacteria (Helicobacter
pylori)
–Churning produces acid chyme
–Closed at esophagus end by
cardiac orifice
–Closed to small intestine at
pyloric sphincter
Figure 41.15 Secretion of gastric juice
• Small Intestine
–Longest section of canal
–Where most absorption occurs
–First 25 cm = duodenum
–In duodenum
•digestive juices from pancreas,
liver, gall bladder, and gland
cells enter
• Pancreas
–Produces hydrolytic enzymes and
bicarbonate (to reduce acidity)
• Liver
–Production of bile (with bile salts)
that aids in digestion of fats
• Gall bladder
–Stores bile
Figure 41.16 The duodenum
• Small Intestine (in duodenum)
•Carbohydrate digestion
–Pancreatic amylases
hydrolyze polysaccharides
•Protein Digestion
–Trypsin and
Chymotrypsin break
bonds between certain
amino acids
–Carboxypeptidase splits
off one amino acid at a
time at carboxyl end
–Aminopeptidase chops
off one amino acid at
amino end
–Dipeptidase,
enteropeptidase also
involved
•Fat digestion
–Fat insoluble in water
–Bile salts emulsify fat
droplets to keep them
from coalescing
–Lipase hydrolyzes fat
•Nucleic acid digestion
–Nucleases
Figure 41.17 Enzymatic digestion in the human digestive system
Figure 41.18 Activation of protein-digesting enzymes in the small intestine
– Absorption of nutrients (mostly in
jejunum and ileum)
– Increased surface area by villi and
microvilli
– Each villi contains capillaries and
lacteal (small lymphatic vessel); each
only one cell thick
– Nutrients move via diffusion and
active transport
– Fats move into lacteal
– All other nutrients empty into
capillaries and eventually move into
hepatic vessel to liver
Figure 41.19 The structure of the small intestine
• Large Intestine (colon)
–Connected to small intestine at Tshaped junction
•One arm is cecum that leads
to appendix in humans
•Other arm is the colon
–Reabsorbs water
–Leftover waste is feces
–Feces stored in rectum and
released through anus
–E. coli in colon
Figure 41.x1 Large intestine
EVOLUTIONARY ADAPTIONS
• Teeth vary according to what
the animal eats
–Fangs, incisors, canines,
“grinders”
• Herbivores and omnivores
longer alimentary canals
than carnivores due to
cellulose digestion
Figure 41.20 Dentition and diet
Figure 41.21 The digestive tracts of a carnivore (coyote) and a herbivore
(koala) compared
• Special chambers to digest
cellulose with help of
prokaryotes and some
protists
–Ruminants (examples:
cattle and sheep)
Figure 41.22 Ruminant digestion
Figure 41.x2 Termite and Trichonympha