Nutrition and Digestion

ResourcesLecture: 2009, Dr. Sylvia Kehoe, UW—River Falls

Textbook: The Veterinary Technician’s Pocket Partner, Marisa BauerResources

Walter J. TaylorAgricultural Educator and Co-FFA Advisor

Plymouth Comprehensive High School

www.consumer-supply.com

general terminology• Nutrition: how an organism assimilates food and uses it for growth and

maintenance

• BMR (Basal Metabolic Rate): the amount of energy consumed at rest

• Calorie: a unit of energy consumed by the body

• Nutrients: a chemical element or substance essential for supporting life (maintenance, growth, reproduction, lactation, gestation, and immunity

• Homeostasis: biological systems that maintain stability for optimal health and survival

• Metabolism: a collection of chemical reactions , takes place in the body’s cells, converts the fuel in the food consumed into the energy needed to power everything an animal does. If metabolism stops, a living thing dies.

why is nutrition important?• It is the basic life system of animals

• A large portion of the cost of having/raising animals

• There is a demand for nutritionists

• History: the 18th century scientist, Antoine Lavoisier, was nicknamed the “Father of Nutrition” because of his thinking of why kids died while consuming various diets. He researched metabolic rates on guinea pigs, which were placed in a cold box and observed data on heat production in relation to diet.

six components of food* Please leave room in your notes for descriptions• Water• Fats• Protein• Carbohydrates• Ash/minerals• Vitamins

Water• Primary Nutrient• 10% water loss is really serious• 15% water loss is incompatible with life• Found inside and outside of cells• Lubes the body• Aids body temperature by absorbing heat and moves it

away from the body’s tissues• 70% of body composition• Carries nutrients, by-products, and waste through the body• A fluid medium for the blood and lymph system• A component of every biochemical reaction in the body

Terms• Digestion:

– chemical breakdown of food/feed outside the body

• Prehension: – how an animal obtains food/feed

• Lips, trunks, beaks, tongues, hands, feet

• Mastication: – chewing, the physical breakdown

of food/feed• Absorption:

– Uptake of nutrients into body tissue

– Passage across epithelial cells

• Metabolism:– Net process of anabolism and

catabolism– Anabolism: build up of tissues– Catabolism: break down of

tissues• Ration:

– mixture of food/feed stuffs to supply nutrient for a day

• Diet:– a ration over a longer period

of time

The Gut• Alimentary Track– From the mouth to the anus

• Gastrointestinal Track (GIT)– From the stomach to the colon

The Gut• Mouth– Prehension, teeth structure– Omnivores

• Use incisors to bite and molars to grind– Carnivores

• Use incisors to tea and molars to crush meat• Worst chewer

– Herbivores• Use incisors to cut plants and molars to grind• Best chewer

– Birds• Have beaks to gather feed, swallow, gizzard grinds feed

The Gut• Mouth– Salivary Glands• Aid in chemical and physical breakdown of food/feed• FOUR parts

– Mucous: lubricates the food/feed– Water– Salivary amylase: enzymes that breaks down starch/amylase

bonds– Sodium bicarbonate: neutralizes pH / reduces acidity

• THREE locations– Sublingual salivary glands: under the tongue– Submaxillary/Submandibular: at the base of the jaw/tongue– Parotid: in cheek below the ear (largest of the three)

The Gut• Mouth/ Esophagus– Deglutition

• Swallowing– Esophagus

• Mouth to stomach connection• Circular muscles and longitudinal muscles• Connects to the stomach via the cardiac sphincter

– Peristalsis • Involuntary movement of muscles acting on moving food/feed

through the alimentary and GI tracks– Food entering the esophagus is called a bolus, “little

round ball”

The Gut• Stomach– Physical and chemical breakdown of food/feed– No absorption except alcohol molecules– THREE Parts

• Cardiac region: upper region of the stomach, secrets mucous to protect this region

• Fundic/Gastric region: center region of the stomach– Peptic cells secrete the enzyme pepsinogen, which is the precursor to zymogen,

which is produced when HCl and pepsinogen react, pH is lowered becoming more acidic

– Chief cells secrete HCl “Hydrochloric acid”, they are stimulated by food/feed coming into the stomach

• Pyloric region: lower region of the stomach that secrets mucous to protect this lower region, connects to the small intestine via the pyloric sphincter

The Gut• Stomach– Doctors Marshall and Warren found Heliobacter

plyorii living in the stomach wall. • Causes stomach ulsars• Is consumed a lot, but only affects animals and people if

environmental factors are prevelent, (ie: stress, a weak immune system, etc.)

The Gut• Small Intestine (SIN)– THREE parts• Duodenum: the first part of the SIN, mucous is secreted,

chyme/ingesta entering this region trigger enzymes and secretions– Chemical digestion begines

• Jejunum: some chemical digestion occurs, absorption mainly occurs, is the largest section of the SIN• Ileum: absorption of any remaining nutrients occurs

– By-products: grand father clocks, strings on instruments, food casings

The Gut• Small Intestine (SIN)– There are three layers of the SIN:• Outermost layer is comprised of connective tissues that

contain: nerves, blood vessels, collagen, etc.• Middle layer is called the muscularis layer• Inner most layer is called the mucosa

– Villi are finger like projections made up of enterocytes (epithelial cells found in the intestines)

– SIN is constantly shedding cells making up the villi» The bottom groove of the villi is called the crypt where

enterocytes are actively dividing every 72 hours or every 3 days before they are discarded

The Gut• Small Intestine (SIN)– Enterocytes• Produce also produce enzymes

– Maltase breaks down maltose into the molecules: glucose + glucose

– Lactase breaks down lactose into the molecules: glucose + galactose

– Sucrase breaks down sucrose into the molecules: glucose + fructose

The Gut• Pancreas: secrets digestive juices directly in the

duodenum– Acts like:• Endocrine gland: has no storage and secrets directly into

the blood• Exocrine gland: has storage and secrets into the blood or

outside the body (into the GIT)– Digestive juices:

» Pancreatic amylase: digests amlyose (starches)» Pancreatic lipase: digests lipids

The Gut• In the Duodenum– Breaks down protein…these are zymogens• Trypsinogen converts to Trypsin• Enterocytes make enterokinas

– With trypsin activates the following conversions:» Chymotrysinogen to chymotrypsin» Proelastase to electase» Procarboxypeptidase A to carboxypeptidase A» Procarboxypeptidase B to carboyzpeptidase B

The Gut• In the Duodenum– Breaks down protein…these are zymogens• Cholesystokinin (CCK): a hormone that is secreted due to

food/feed (proteins/lipids) entering the duodenum– Causes the pancreas to secret digestive juices– Causes the gall bladder to secrete bile– Also binds to receptors that tell your brain that you/animal is full

• Bile: stored in the gall bladder, produced in the liver– FOUR parts

» Bile salts: emulsify lipids» Bile pigments: dark-green color» Cholestrol» mucous

The Gut• Three types of absorption– Simple Diffusion: no energy, small, simple molecules– Facilitated Diffusion: transporter/channel, no energy– Active Transport: transporter/channel, energy is used,

uses sodium/potassium channels

– *Passive transfer: occurs only in young animals, ruminants less than 72 hours old• Large molecules can be absorbed w/out breaking them into

small molecules– Ex: immunal globules, because calves are born w/out an immune

system

The Gut• Large Intestine: (LI)– THREE parts• Cecum: blind pouch, houses microbes like fungi, protizoa

and bacteria• Colon: houses bacteria, the main function is to absorb

water and digest roughages– Has cuboidal cells + goblet cells that secrete mucous– Bacteria produce volatile fatty acids (VFAs) which are used for

energy production in the body• Rectum: controls passage of undigested material called

feces

• Anus: anal sphincter controls the exiting of feces

The Gut (TBC)• Horses: hind-gut fermenters• Ruminants: Rumen• Birds: