Animal Nutrition Final (ALL)

Roles of digestive tract

• Acquisition of food

• Absorption of nutrients

• Protection from foreign invaders

• breakdown of feeds into absorbable nutrients

• elimination of waste

mastication

• chewing

• goal: to reduce particle size of feed

prehension

taking food/water into mouth

major roles of saliva

• Moistens feed

  • Provide ions & water

  • Lubricate to aid in swallowing

• Produces salivary amylase

  • Aids in starch digestion

  • Not secreted in ruminant saliva

• Specialized functions

  • Draculin in vampire bats

    • Prevents blood from clotting

3 major salivary glands present in the mouth of an animal

• Parotid

  • Type: serous (watery)

  • Main components: water, enzymes, ions

  • lubrication

• Sublingual

  • Type: mucosal

  • Main component: mucus

  • Protection of irritation of skin linings

• Submaxillary

  • Type: mixed

  • Main components: mucus, ions, enzymes, water

deglutition

• Swallowing

• Reflex initiated by presence of food in the pharynx

• Propulsion of food to stomach by esophageal peristalsis

peristalsis

• Process animal uses to move through the digestive tract

• Sequential muscle contractions that push food through digestive tract

major roles of the stomach

• Storage of food

  • Control release of digest into small intestine

  • Control passage rate throughout digestive tract

• Initial breakdown of food

  • Mechanical

  • Acid

  • Enzymatic

• Regulates hunger

What hormone(s) are secreted by the stomach? 

• Pepsin (proteolytic hormone)

  • Responsible for breaking down protein

• Grehlin

  • growling/responsible for immediate drive for hunger

  • Short term regulation of hunger

3 regions of the stomach

• cardiac

• fundic

• pyloric

cardiac region

produces mucus for lubrication and protection

fundic

• Produces hydrochloric acid and enzymes

  • Parietal cells

  • Chief cells

pyloric

• End of digestion tract

• Secretes hormones and mucus

which cells secrete hydrochloric acid

parietal cells

which cells secrete pepsinogen

chief cells

zymogen

non-activated hormone that must be activated by something

major roles of small intestine

• Produces enzymes

• Produces bile acids

  • Responsible for fat absorption

• Produces hormones

What is the role of the gall bladder, what is stored there, and what do those stored molecules do within the digestive process?

• Role: to store bile so that it can be released later

• Stored: bile

• What they do: breaks down fats into smaller particles

3 sections of the small intestine

• (first) duodenum

• jejunum

• (last) ileum

duodenum

• Enzyme secretion

• Bile secretion

• Absorption

jejunum

absorption

Ileum

• Transition from small to large intestine

• Less absorption

• Immune cells

Which section of the small intestine is densely populated by immune cells?

Ileum

What structures in the small intestine exist to increase the surface area for absorption

villi

Define emulsification in the context of lipid digestion

Process of taking big fat particles & adding amphipilic molecules and then breaking up the big fat particles into smaller fat particles

which secretions from the liver/gall bladder play a role in emulsification

• Pancreas secretes digestive enzymes to break down feeds

  • Metabolic hormones (insulin)

  • Bicarbonate salts to buffer small intestine

  • Glucagon 

• Bile is produced in liver and stored in gallbladder, released into duodenum

major roles of large intestine

• Resorbs water from GIT

• Microbial fermentation

What is secreted into the large intestine to aid in digestion? 

mucus

What is secreted into the small intestine to aid in digestion? 

bile

What is secreted into the stomach to aid in digestion? 

hydrochloric acid, pepsin

3 sections of large intestine

cecum, colon, rectum

cecum

• First section

• Microbial fermentation/creates stable fermentation area, slow rate

• Most active part

• Most absorption occurs

colon

• Second section

• Some absorption of short chain fatty acids

rectum

• Last section

• Regulates excretion of feces

Which molecules are starch broken down into

maltose, glucose

enzyme that breaks down protein

pepsin

enzyme that breaks down fat

lipase

enzyme that breaks down starch

amylase

Which glucose transporter brings glucose into an enterocyte

SLGT1

Which glucose transporter brings fructose into an enterocyte

GLUT5

Which glucose transporter moves glucose from the enterocyte to circulation

GLUT2

role of gastrin in digestive tract

• stimulates HC: and pepsin production

• secreted by stomach

role of ghrelin in digestive tract

• increases hunger signaling

• secreted by stomach

• major short term hunger signal

CCK & feed intake

• decreases food intake

• causes the release of digestive enzymes and bile into small intestine

• secreted by duodenum

PYY & feed intake

• decreases food intake

• increases retention in the intestine

• increases water & electrolyte absorption

• secreted from duodenum & jejunum

role of incretins in nutrient metabolism

to sense nutrients to prime insulin signaling

incretin examples

• GLP-1: increases insulin signaling & retention in intestine, decreases food intake

• GLP-2: increases intestinal growth

• Glucose-dependent insulinotropic hormone: stimulates insulin secretion & inhibits GI motility

How does the saliva of dairy cows differ from pigs

• Cows: continuous saliva production-25 to 40 gallons per day

• Pigs: saliva is lower in volume, functions more as a lubricant

• Sheep: produces 2 gallons of saliva per day

rumination

regurgitation and rechewing of a bolus of food (called cud) to further mechanically break down fibrous feeds & increase surface area for microbial digestion

• stimulates additional buffering through saliva production

why do ruminants perform rumination

to help rechew their food, stimulates saliva production, undergo fermentation

4 compartments of a ruminant stomach

rumen, reticulum, abomasum, omasum

rumen

undergo lots of fermentation

reticulum

trap larger feed particles & regulate the flow of nutrients down to the lower digestive tract

abomasum

secretes HCL & pepsin and begins the degradation of protein

omasum

absorbs residual water and VFAs

3 major volatile fatty acids produced in the rumen

butyrate, propionate, acetate

how are VFA used by the animal

used as primary energy source

What structures in the rumen exist to increase surface area for absorption

papillae

4 major microbial groups in the rumen of ruminants

• Bacteria: 90% of rumen microbial genetic diversity, 7000 species

• Archaea: methanogens, 1500 species

• Protozoa: 50% total mass of rumen microorganisms

• Fungi: 6 genera, 18 species

which microbial group has the most genetic diversity

bacteria

why can’t horses vomit

Because their esophagus only allows one-way peristaltic movements

Horses are missing an organ that releases stuff into the small intestine. What is the organ they are missing, what stuff does it release, and how does the lack of this organ affect horse digestion?

• Missing organ: gallbladder

• Release: bile

• Affect digestion: less bile secreted, less lipid digestion

How does hindgut acidosis lead to inflammation and potentially laminitis in horses?

if too much starch is fed

which organ is enlarged in horses that helps it digest fiber?

cecum

What is the function of the crop in the chicken digestive tract

• Allows breakdown by salivary amylase

• Moistens digesta

• Regulatres flow of food to lower GIT

function of the proventriculus in the chicken digestive tract

true stomach, production of HCL & pepsin

function of the gizzard in the chicken digestive tract

Pepsin and HCL from proventriculus secretion will be mixed with feed in gizzard and aid in digestion

What are the differences in the way chickens excrete nitrogen compared to mammals?

• chickens: excrete uric acid

• mammals: excrete urea

What is the difference in the large intestine between avian species and mammals?

• Avian: 2 cica

• Mammals: 1 cica

7 physiological roles of lipids

• Provide long-term energy storage,

• Cell signaling,

• Formation of steroid hormones (Cortisol, Testosterone, Estrogen, Progesterone),

• Formation of vitamin D,

• Bile acid,

• Inflammatory signals (eicosanoids/oxylipins),

• Provide cellular structure,

• Provides insulation for nerve cells

general structure of a triglyceride

glycerol back bone and 3 fatty acid tails

general structure of a diglyceride

glycerol backbone and two fatty acids

monoglyceride

glycerol backbone and 1 fatty acid tail

difference between a “free fatty acid” and an “esterified fatty acid”

• free fatty acid: chain of carbon molecules with methyl and carboxyl end

• esterified fatty acid: formed an ester bond with a glycerol molecule

which type of fatty acids are pro-inflammatory

omega-6

which type of fatty acids are anti-inflammatory

omega-3

which end of a fatty acid do you begin counting from using the delta counting scheme?

count from carboxyl end

which end of a fatty acid do you begin counting from using the omega counting scheme?

count from methyl end

cis double bond and a trans double bond

• cis is more of a hexagonal shape

• trans is like a squiggle

C16:0

palmitic acid

C18:0

stearic acid

C18:1

oleic acid

C18:2

linoleic acid

C18:3

linolenic acid (essential, omega-3)

C20:4

arachidonic acid (conditionally essential, omega-6)

C20:5

EPA (conditionally essential, fish oil, omega-3)

C22:6

DHA (conditionally essential, fish oil, omega-3)

antidioxants prevent which type of rancidity of fats

oxidative rancidity

rank the following animal species by their fat requirement: cats, pigs, horses, ruminants

highest: cats, pigs, horses, ruminants : lowest

saturated fats

no double bonds between carbon atoms in fatty acid chains

• saturated with hydrogen atoms

unsaturated fats

1 or more double bonds (kinks) between carbon atoms

• have fewer hydrogen atoms than saturated fats

symptoms of a dietary fat deficiency

• reduced growth & feed deficiency

• poor reproductive performance

• skin lesions, hair loss, poor feathering

• subcutaneous hemorrhage

what are the 3 essential fatty acids in all animals

linoleic, linolenic, arachidonic

orexigenic

• signals that stimulate food intake

• induces animals to eat more

anoerexigenic

tells the animal to stop eating, shuts down feed intak

hunger

feeling of discomfort or weakness caused by a lack of food with the desire to eat

satiety

satisfied feeling of being full after eating

satiation

completely satisfied to the point where a need or desire is no longer felt, often to the point of feeling weary or overindulged

From an animal standpoint, what is generally the major factor driving feed intake

• All senses: sight, smell, taste, texture, temperature, sound

• Food characteristics / palatability

• Other animals, “feeding time”

• Social pressure

• Environmental discomfort

which region of the brain integrates feed intake signals to regulate hunger and satiety

hypothalamus