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DIGESTION. ANSC 101. Definition. Digestion is all of the chemical and physical changes that food undergoes to be absorbed. Absorption takes place as nutrients enter the body from the digestive tract. Mouth Esophagus Stomach Small intestine Large intestine. Liver, gall bladder

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Digestion

DIGESTION

ANSC 101


Definition
Definition

  • Digestion is all of the chemical and physical changes that food undergoes to be absorbed.

  • Absorption takes place as nutrients enter the body from the digestive tract.


Gi tract digestive system

Mouth

Esophagus

Stomach

Small intestine

Large intestine

Liver,

gall bladder

pancreas

GI Tract – Digestive System


Mouth
MOUTH

  • Teeth

  • Tongue

  • Salivary glands


Esophagus
Esophagus

  • Birds

    • CROP

  • Mammals


Stomach
Stomach

  • Complexity varies

    • Simple in monogastrics (nonruminants)

    • 4-chambered complex stomach of ruminant


Functions of stomach
Functions of Stomach

  • STORAGE

  • Chemical Digestion


Non ruminant stomach
Non-Ruminant Stomach

  • 4 regions

    • Esophageal

    • Cardiac

    • Fundic

    • Pyloric


Poultry
Poultry

  • “Stomach” is called PROVENTRICULUS

  • Has same functions as mammal


Gastric secretions
Gastric Secretions

  • HCL

    • Activates pepsinogen to pepsin

    • Does some digestion itself

  • Gastric Enzymes

    • Pepsin

    • Lipase

    • Renin

  • Mucin

  • Intrinsic Factor (for absorbing B12)


Ruminant stomach
Ruminant Stomach

  • 4 compartments

    • Rumen – big fermentation vat

    • Reticulum – “hardware stomach”

    • Omasum – “many plies”

    • Abomasum – “true stomach”


Rumen microbiology
Rumen Microbiology

  • Bacteria do 3 things

    • Digest CHO to VFA’s (including cellulose)

    • Remodel proteins, manufacture essential amino acids and utilize NPN

    • Manufacture B vitamins


Summary of rumen action
Summary of Rumen Action

  • CHO ——> VFA’s

  • Proteins ——> Bacterial protein

  • Fats ——> hydrogenated but not much utilization

  • B Vitamins ——> synthesized

  • Vitamins ADE ——> needed in diet


Small intestine
Small Intestine

  • Duodenum

  • Jejunum

  • Ileum


Digestive juices
Digestive Juices

  • Bile

    • Produced in the LIVER

    • Stored in the Gall Bladder

  • Pancreatic juice

    • Exocrine secretions

      • Sodium carbonate and bicarbonate

      • Enzymes

    • Endocrine secretions

      • Insulin

      • Glucogon


Digestive juices continued
Digestive Juices continued

  • Secretions from small intestine wall

    • They digest disaccharides, peptides, etc to forms that can be absorbed


Absorption
Absorption

  • Molecules must get from gut lumen into brush border of epithelial cells, then across cells into blood or lymph.

  • Occurs by diffusion, facilitated absorption and active absorption.


Large intestine
Large Intestine

  • Ascending, transverse and decending colon

  • FUNCTIONS:

    • Storage

    • Absorption of water

  • Special role of cecum


Cecum
Cecum

  • Blind pouch at junction of small and large intestine

  • Developed in nonruminant herbivores (horses, rabbits)

  • Provides post-absorptive fermentation vat

    • Digests cellulose, Does NOT provide protein



Metabolism defined cho
Metabolism defined | CHO

  • Use by the body of nutrients and metabolites

  • Carbohydrates – converted to tiny amounts of glycogen, used for blood sugar, or converted to ATP (energy), stored as fat


Metabolism of fats
Metabolism of Fats

  • Go to liver, then to fat storage, or used for energy


Metabolism of proteins
Metabolism of Proteins

  • Amino acids enter blood stream and supply cells with amino acids for protein synthesis

  • Amino acids not quickly used are deaminated and used for energy


Metabolism of energy
Metabolism of Energy

  • Energy in the chemical form of ATP is either used by the tissues or stored in animals as fat


Metabolism of vit s minerals
Metabolism of Vit’s & Minerals

  • Vitamins are involved in tissues throughout the body, maintaining structures and participating in chemical reactions

  • Minerals make up structural components and activate enzymes, maintain water balance, and more.


End of digestion 101
End of Digestion, 101

  • Next we will consider where animals will GET those nutrients:

  • FROM FEEDS


Animal feeds
Animal Feeds

  • 2 major catagories of energy-providing feeds are:

  • Concentrates

  • Roughages


Concentrates
Concentrates

  • Grains

    • High in energy, low in fiber, low in protein, low protein quality

  • Protein supplements

    • From oil seeds (like soybean meal)

    • From animal byproducts, fish byproducts, etc.


Roughages
Roughages

  • Not used or used poorly by nonruminants

  • CATAGORIES

    • Grasses

    • Legumes

    • Crop residues


Grasses
Grasses

  • Grow “everywhere”

  • Moderate energy source

  • Low protein source

  • Low calcium levels

  • Good for meeting maintenance needs


Legumes
Legumes

  • Moderate sources of energy

  • High protein levels

  • High calcium levels

  • Not adapted to grow well everywhere

  • Where they do grow, they increase soil fertility


Legumes1
Legumes

  • Alfalfa

  • Red clover

  • White clover

  • Sweetclover

  • Alsike


Crop residues
Crop Residues

  • Provide bulk

  • Some but low levels of energy

  • Useful in helping meet maintenance

  • Very cheap except for processing and transportation costs



Forages can be fed as
Forages can be fed as:

  • Pasture

  • Hay

  • Silage





Ration balancing
Ration Balancing

  • The task of meeting the animals nutrient requirements with the feeds provided to the animal


Ration balancing1
Ration Balancing

  • Determine animal’s requirements

    • From NRC, Extension publications, etc.

  • Get feed’s nutrient content

    • From analysis or feed tables

  • DO THE MATH

    • By hand or

    • By computer program


Example by hand
Example by Hand

  • Say pig needs 16% CP, & using Corn with 8% CP and Suppl. with 36% CP.

    16 = .08X + .36(100-X)

    16 = .08X + 36 - .36X

    16 – 36 = .08X - .36X

    - 20 = - .28X

    X = -20X/-.28X = 71.4% corn

    100 – X = 28.6% supplement



Feeding programs
Feeding programs

  • Pigs and poultry are fed primarily “simple” diets based on corn for energy, SBM for protein, and fortified with vitamins and minerals.

  • Full feed growing/finishing pigs

  • Limit feed pregnant sows & gilts

  • Use antibiotics judiciously


Beef and sheep
Beef and Sheep

  • Summer rely on range, pasture when possible

  • Winter: need preserved feeds:

    • Hay

    • Silage

    • Grain as needed



Feeding beef cows
Feeding Beef Cows

  • For MOST, that means:

    • Spring & summer = Pasture

    • Fall – Winter = Preserved feeds

    • Late Winter (late gestation) supplement

      • Grain

      • Protein as needed

    • Test hay to know what you are feeding



Feeding dairy cattle
Feeding Dairy Cattle

  • Requirements are very high due to high milk production

  • Intake is high (4% BW vs ~2% for beef)

  • Feed grain for high production (up to 60% of total DM)


Dairy feeding
Dairy feeding

  • Must maintain at least 40% forage in the ration



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