Fundamentals of Small Animal Nutrition

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Fundamentals of Small Animal Nutrition

• Digestion and Absorption
• Dr. Randy Ackman

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Digestion

• Digestion
• Large complex molecules are broken down into
  smaller subunits
• Polymers to monomers
• Allows the animal to utilize the simplest form of
  complex molecules.
• Absorption
• The entrance of nutrients into the body

http//courses.cm.utexas.edu/jrobertus/ch339k/over
heads-3/ch15_digestion.jpg
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Digestion

• Digestive Process
• Ingestion
• Mechanical digestion
• Propulsion
• Chemical digestion
• Absorption
• Defecation

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Digestion

• Digestion
• Mechanical
• Physical activity
• Mastication
• Peristalsis

http//www.wkyc.com/images/news/020513dogfood.jpg
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Digestion

• Mastication muscles
• Temporalis
• Mandibular branch of V
• Masseter
• Mandibular branch of V
• Digastricus
• Mandibular branch of V
• Facial nerve VII
• Pterygoids
• Mandibular branch of V

http//137.222.110.150/calnet/HN/page3.htm
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Digestion

• Digestion (mechanical)
• Peristalsis
• Propulsion
• Aboral
• Bolus stimulates mechanoreceptors
• Longitudinal muscle contracts
• Ileus
• Prokinetics
• Segmentation
• Contraction of circular muscle

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http//www.cals.ncsu.edu/course/zo250/lab1-dissect
ion.html
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Digestion

• Digestion
• Chemical
• Enzymatic
• Splitting chemical bonds via hydrolysis reactions
• CHO ? simple sugars
• Lipids? glycerol fatty acids
• Proteins ? amino acids and dipeptides
• pH
• Denaturation of protein
• Read Table 7-1 pg 54

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http//www.fed.cuhk.edu.hk/johnson/misconceptions
/concept_map/digest.gif
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Digestion

• Mouth
• Ingestion
• Mastication
• Saliva mixed with food
• Pavlov
• Lubricates food aids in
• Chewing
• Swallowing
• Aqueous environment to stimulate taste buds
• No amylase
• Carnivores
• Dog cats

http//www.vetmed.wsu.edu/ClientED/anatomy/dog_dig
est.asp
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Digestion

• Dentition
• Equal number of incisors and dogs and cats
• Dog more premolars and molars
• Omnivore
• Cat less premolars and molars
• Obligate carnivore

http//www.catinfo.org/Meat20Grinder20and20Robb
ie20-20web.jpg
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Digestion
http//arbl.cvmbs.colostate.edu/hbooks/pathphys/di
gestion/pregastric/dentalanat.html
http//arbl.cvmbs.colostate.edu/hbooks/pathphys/di
gestion/pregastric/catpage.html
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Digestion

• Esophagus
• No digestion
• Conduit from mouth to stomach
• Mucus cells
• Lubricate bolus
• Cardiac sphincter
• Regulates entrance of food into stomach

http//littlecrittersvet.com/ipw-web/gallery/rads/
DSC00992_1
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Digestion

• Stomach
• Mechanical
• Very muscular organ
• Reservoir
• Mixes ingested food with gastric secretions
• Mucous glands
• Protect gastric mucosa

• Chemical
• Parietal cells
• HCl
• Activates pepsinogen
• Provides optimal environment
• Denatures protein
• Chief cells
• Pepsinogen
• Acitvated by HCl to pepsin
• Hydrolysis of protein to smaller peptides

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Digestion
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Digestion

• Stomach secretions
• Cephalic
• Anticipation of eating
• Sight, smell of food
• Gastric
• Presence of food in stomach
• Intestinal
• Entrance of food into the proximal duodenum

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Digestion

• Gastrin
• Increases release of gastric secretions and
  increases gastric motility
• Released by presence of food and distension of
  stomach
• Enterogastrone
• Released by the presence of fatty foods in
  proximal duodenum
• Inhibits acid production
• Reduces motility

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Digestion

• Stomach
• End product
• Chyme
• Acidic in nature
• Semifluid mass
• Passes through pyloric sphincter
• Enters small intestine
• Emptying of chyme / gastric contents
• Osmotic pressure
• Particle size
• Volume
• Acidity

• Large meals
• Slower emptying
• Liquid meals
• Leave stomach faster than solids
• High fat diets
• Decrease gastric emptying
• Soluble fiber
• Decreased gastric emptying than compared to
  insoluble fiber

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Digestion and Absorption

• Small Intestines
• CHOs and fats not changed
• Proteins
• Broken to smaller polypeptides
• Site of majority of digestion and absorption

• http//www.sirinet.net/jgjohnso/villliabsorption.
  jpg

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Digestion and Absorption

• Brunners glands
• Aka duodenal glands
• Secrete alkaline mucous
• Rich in bicarbonate
• Neutralizes acidic chyme entering small
  intestines

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Digestion and Absorption

• Pancreas
• Enzymes
• Trypsinogen
• Activated by enterokinase
• Chymotrypsin
• Carboxypeptidase
• Nuclease
• Pancreatic lipase
• Amylase
• More in the dog than cat
• Cholesterol esterase
• Bicarbonate salts

http//www.leerburg.com/pancreatic.htm
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Digestion and Absorption

• Small intestines
• Enzymes
• Intestinal lipase
• Aminopeptidases
• Dipetidases
• Nucleotidase
• Nucleosidase
• Enterokinase
• Brush border
• Maltase
• Lactase
• Sucrase

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Digestion and Absorption

• Bile
• Does not digest
• Emulsifies fat
• Forms micelles
• Water soluble
• Increases surface area
• Activates lipases
• Facilitates absorption of lipids

http//www.chem.ucalgary.ca/courses/351/Carey5th/C
h26/ch26-1-2.html
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Digestion and Absorption

• Hormonal control of digestion
• Secretin
• Stimulate by acidic chyme entering small
  intestines
• Causes release of bicarbonate from pancreas
• Controls flow rate of bile from gallbladder
• Cholecystokinin
• Released by proximal small intestines
• Released in response to presence of fat
• Stimulates
• Stimulates pancreatic secretions
• Contraction of the gallbladder

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Digestion and Absorption

• Chemical digestion
• Completed in small intestine of dog and cat
• Amino acids, dipeptides, monosaccharides,
  glycerol, free fatty acids, monoglycerides,
  diglycerides
• Absorption
• Transfer of nutrients
• From lumen of intestines
• To blood or lymphatics

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Absorption

• Absorption
• Greatest surface area
• Mucosal folds
• Villi
• Microvilli
• 600 X than serosal surface
• Lacteal
• Centrally located in villous
• Contains
• Capillary
• Lymphatic vessel

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Absorption

• Absorption
• Passive diffusion
• Osmotic gradient
• Electrolytes
• Water

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Absorption

• Facilitated diffusion
• Carrier proteins
• Located in membranes

http//www.sirinet.net/jgjohnso/passivetrans1.jpg
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Absorption

• Active transport
• Requires energy expended by cell (enterocyte)
• Against a concentration gradient
• Most monosaccharides absorbed this way
• Tied to sodium pump
• Carrier protein

http//www.mednote.co.kr/images/microvilli.jpg
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http//www.mednote.co.kr/images/microvilli.jpg
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Absorption

• Liver
• Portal circulation brings
• Amino acids
• Sent into circulation
• Excess
• Converted to nonessential aa
• Metabolized for energy
• Monosacchrides
• Converted to glycogen for storage
• Sent into circulation

http//www.elmhurst.edu/chm/vchembook/images/590m
etabolism.gif
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Absorption

• Minerals
• Most in ionized form
• Water soluble vitamins
• Passive diffusion
• B12
• Requires intrinsic factor from stomach
• Fat
• Soluble vitamins
• Combine with bile salts
• Normal fat absorption normal fat soluble
  vitamin absorption

http//www.mednote.co.kr/images/microvilli.jpg
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Absorption

• Large Intestine
• Ileocecal valve regulates entrance into large
  intestines from small intestines
• Shorter in cat, longer in dog
• Dog and cat
• Vestigial cecum
• Bacteria digestion of dietary fiber
• Small compared to non-ruminant herbivores
• Creation of SCFA
• Provide energy for colonocytes

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Absorption

• Large Intestine
• Absorption of electrolytes and water very
  efficient
• No villi
• No active transport mechanisms for absorption
• Bacteria of large intestine
• Undigested protein
• Indole, skatole, hydrogen sulfide H2S fecal
  odor
• Undigested carbohydrates (legumes, soybeans)
• Gas or flatulence
• Hydrogen, carbon dioxide, methane

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Absorption

• Large intestine
• Feces
• Undigested food residue
• Sloughed cells
• Bacteria
• Unabsorbed endogenous secretions
• Water