digestive system of animals animal science frameworks presentation unit 3.1
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Digestive System of Animals Animal Science Frameworks
Presentation Unit 3.1
Mr. Sullivan
Digestion
Purpose: reduce feed particles to molecules that can be absorbed into the blood
• Mechanical breakdown of food– chewing
• Chemical breakdown of food– HCl in the stomach– enzymes
• Contractions of digestive tract
Animals are classified by the types of food they ingest
• Carnivore - animal products– Dogs, Cats
• Herbivore - plant products– Cattle, Sheep, Goats, Horses
• Omnivore - combination of plant and animal products– humans, pigs
Animals are also classified by the type of stomach they have
• Monogastrics or non-ruminants• Ruminants
Monogastric Animals
Monogastric – one or simple stomach structure
• mostly carnivores and omnivores» Very simple: mink and dog» Cecal digestion: horse, rabbit or rat» Sacculated stomach : kangaroo
Ruminant Animals
Ruminant - 4 compartment stomach with the compartments before the “true” stomach
• herbivores» cattle, sheep, goats and pseudoruminants (llamas)
Digestion
• Prehension– Bringing the food to the mouth
• Upper limbs, head, beak, claws, mouth, teeth and lips
• Mastication or chewing– To crush the food, increase surface area and
allow enzymes to act on molecules• Carnivores need only to reduce the size of the particle• Herbivores must chew continuously (40-50,000 times
a day)
Monogastric Animal Digestive Tract
Basic anatomymouth
stomachsmall intestine
large intestine or colon
Monogastric Animal Digestive Tract
• Feed passes from the mouth to the stomach through the esophagus
• To reduce the size of the feed particles
• From the stomach it passes through the– duodenum (first part of the small intestine)
• Bile and pancreatic secretions enter here– jejunum (second part of the small intestine)
• Absorption of nutrients– ileum (third part of the small intestine)
• To split food molecules and absorb nutrients
Monogastric Animal Digestive Tract
• Large Intestine• water absorption• feces formation
• Rectum
Human and Pig Similarities
• Both are omnivores• Cannot synthesize B complex vitamins• Cannot synthesize amino acids• Can become obese with increased food
intake
Monogastric Animal Digestive Tract
• Exceptions– herbivores
• horses have a cecum (blind anterior end of the colon) where feed is fermented
– Cecum is posterior to optimum feed absorption area, thus advantages of the ruminant animal is lost
Enzymes of the Digestive Tract
Enzyme names often end in -ase
and
begin with a description of the substrate they act upon
Enzymes of the Digestive Tract
Enzyme Substrate ProductAmylase Starch Dextrin,
DisaccharidesChymotrypsin Peptides Amino Acid
PeptidesLactase Lactose Glucose
galactose
Enzymes of the Digestive Tract
Enzyme Substrate ProductLipase Lipids Fatty acids
glyceridesPepsin Protein polypeptidePeptidase Peptides amino acidSucrase Sucrose glucoseTrypsin Protein polypeptide
Monogastric Digestion
• Enzymes help breakdown large molecules– Mouth
• amylase in saliva of humans and pigs breaks down starch to disaccharides and dextrin
– Stomach• HCl - creates acidic environment• pepsin - breaks proteins down polypeptides
Monogastric Digestion
• Enzymes help breakdown large molecules– duodenum
• Cells release hormones that act on pancreas and gall bladder
– secretin– pancreozymin– cholecystokinin
Monogastric Digestion
• pancreas– lipase
• lipids to fatty acids and glycerides– trypsin
• proteins to polypeptides– chymotrypsin
• peptides to amino acids and peptides– amylase
• starch to disaccharides and dextrin
Monogastric Digestion
• gall bladder– bile
• produced in the liver• emulsifies fats• alkaline to neutralize stomach contents that are
acidic
• small intestine– amino acids, fatty acids and monosaccharides
are available for absorption
Ruminant Digestion
• mouth• esophagus
• rumen • reticulum • omasum
• abomasum• small intestine• large intestine
Ruminant Digestion
• rumen - 40 gallons in a cow– large fermentation vat– covered with papillae to increase the surface
area– microorganisms digest cellulose – microorganisms synthesize amino acids from
nonprotein nitrogen – microorganisms synthesize B-complex
vitamins
Ruminant Digestion
• reticulum - 2 gallons in a cow– lining looks like a honeycomb– interacts with rumen to mix contents
Ruminant Digestion
• omasum - 4 gallons in a cow– many folds, perhaps to grind feed
Ruminant Digestion
• abomasum - 4 gallons in a cow– true stomach
Ruminant Digestion
• Ruminants eat forage rapidly– they regurgitate food (cud) – and chew it again and swallowed
• Rumination - continuous reguritation, chewing and swallowing
• Eructation - elimination of gases (methane and carbon dioxide) in the rumen from fermentation
Rumen Microorganisms
• Bacteria and Protozoa– rumen environment is moist, warm, and
provides a constant supply of nutrients– entire population of organisms depending on
the kind and quality of the feed– when they are washed out of the omasum into
the abomasum the acidic environment kills the microorganisms
– provide amino acids and some energy
Ruminant Digestion
• Ruminants to not secrete amylase in their saliva
• bacteria and protozoa in the rumen and reticulum utilize starches and sugars- no glucose available for the ruminant– microorganisms do produce volatile fatty acids
(VFA) that are absorbed and converted to energy• acetic, propionic and butyric acids• major source of energy
Energy Pathways in the Ruminant
From Rumen to Abomasum Injestion materials
Cellulose Starch FatComplex SugarsGlucoseVFAs
Energy Pathways in the Ruminant
Liver
VFAsGlucose
Ruminant and Monogastric Absorption in the small intestine• passive transport
– diffusion by concentration• active transport
– villi engulf molecules • to bloodstream or lymph system
Rumen Microorganisms
• Bacteria and Protozoa– rumen environment is moist, warm, and
provides a constant supply of nutrients– entire population of organisms depending on
the kind and quality of the feed– when they are washed out of the omasum into
the abomasum the acidic environment kills the microorganisms
– provide amino acids and some energy
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