VTS 150 Animal NutritionFall 2013Beth Alden, DVMInstructor

Course Objectives Identify the components of the digestive

systems of common companion animals Identify the nutritional needs of common

companion animals Correctly calculate the caloric needs of

companion animals Correctly evaluate a pet food label and

ingredients Identify common toxins for companion

animals

Resources for Class

Textbook:

Nutrition for Veterinary Technicians and Nurses, Ann Wortinger,

Blackwell Publishing, 2007

Resource for Class Case Studies in VeterinaryTechnology Authors Jody Rockett andChani Christensen Students will be requiredto complete assigned casestudies and turn them in

Resources on Library ReserveSmall Animal Clinical

Nutrition 4th Edition, Hand,Thatcher, Remillard, Roudebush,

The Mark Morris Institute, 2000

Students requirements Exams Discussions Toxin project Case studies Final project

Classification of Digestive Systems

Digestive System Connects animals diet with metabolic needs A muscular tube from mouth to anus grinding,

mixing, moving and absorbing nutrients Glands manufacture secretions that are added to the

tube to assist in digestion Ruminants harbor bacteria in the digestive tract that

assist in digestion and synthesis of essential nutrients All animals have microbes in the digestive tract that

assist in digestion, veterinarians are harnessing their power as nutracueticals ( beneficial bacteria administered to animals)

Diet and digestive tract Herbivores – plant eaters Carnivores- meat eaters Ominivores- plant and meat eaters Insectivores – insect eaters Frugivore – fruit eaters ( many species

eat fruit as part of their diets, these animals eat only fruit like some bats)

Digestive tracts The anatomy of the digestive tract is

designed for the type of food the animal utilizes

Carnivores have short digestive tracts that hold a small volume of food

Herbivores have large digestive tracts that hold a large volume

Insectivores and frugivores have digestive tracts that are designed for that diet

Herbivoresvegetation, nitrogen source, minerals and water Difficult to digest, large complex gut is needed- Plant cell walls are hard to break down- Cellulose is the storage form of the plants glucose- Microbes in the gut break down the cellulose and

utilize the glucose to make their energy and volatile fatty acids ( butyric, proprionic and acetic acid)

- The animal utilizes these volatile fatty acids - Very little of the food’s energy is actually absorbed

Carnivores Animal material ( flesh, muscle etc)

makes up the diet More easily digested than herbivore diet GI tract is basically a simple tube Most of the food energy is utilized and

absorbed Mechanical breakdown of food is less

involved

Digestive system types Monogastric- One “true” stomach ( dogs, cats, pigs,

horses) Ruminant- Four compartment stomach- Rumen, reticulum, omasum, abomasum- Cows, sheep, goats

Types of Digestive Systems

Monogastric Stomach Five sections- Cardia- Fundus- Body- Antrum- Pylorus

The Monogastric Stomach1. Cardia Area immediately

surrounding the opening from the esophagus into the stomach

Muscular tone prevents reflux of stomach contents into the esophagus

Source: University of California at Davis

CARDIA

The Monogastric Stomach2. Fundus

Located below the cardia

Blind pouch that distends as food is swallowed

Source: University of California at Davis

FUNDUS

CARDIA

The Monogastric Stomach4. Antrum Grinds up food and

regulates HCl

Also contains glands

BODY

Source: University of California at Davis

FUNDUS

CARDIA

BODY

ANTRUM

G Cells: Gastrin

Mucous Cells: Mucus

The Monogastric Stomach5. Pylorus Muscular ring

(sphincter)

Regulates movement of chyme from stomach into duodenum

Helps prevent backflow of duodenal contents

BODY

Source: University of California at Davis

FUNDUS

CARDIA

BODY

ANTRUM

PYLORUS

DUODENUM

Ruminant Animals

Ruminant Chews food briefly and swallows Regurgitates “cud” to chew again and

swallow ( vital to help break down cellulose)

The stomach is designed to allow this regurgitation and swallowing, plus the action of microbes on the diet ( four compartment stomach)

The Ruminant Stomach Four Compartments:

Reticulum

Rumen

Omasum

Abomasum

Source: University of California at Davis

head tail

Source: University of California at Davis

head

The Ruminant Stomach1. The Reticulum

Smallest, most cranial compartment

Separated from rumen by the ruminoreticular fold

Muscular wall is continuous with the rumen; contract in coordination

tail

RETICULUM

The Ruminant Stomach1. The Reticulum

Honeycombed inside to increase absorptive surface

“Hardware disease”- wires or nails swallowed by animal puncture wall of reticulum

Inside of Reticulum

Source: Colorado State University

RETICULUM

The Ruminant Stomach2. The Rumen

Large fermentative vat(40 - 50 gallon capacity)

Processes plant material into usable energy

Lined with “Papillae”

Made up of series of muscular “Pillars”

Source: University of California at Davis

head tail

RUMEN

The Ruminant Stomach

© University of Bristol, 1988

Pillar PapillaePapillae

Cow Digestive System

The Ruminant Stomach The Rumen

During contractions, pillars close off certain sacs of the rumen which allows mixing of rumenal contents

Mixing of contents essential for fermentative function of rumen

RUMEN

Rumen continued During contractions, pillars close off certain

sacs of the rumen which allows mixing of rumenal contents

Mixing of contents is essential for fermentation in the rumen

Fermentation breaks down the nutrients for the microbes and the animal and produces vitamins B and K

Carbon dioxide and methane are the byproducts of this process

Reticuloruminal contractions Allow “cud” to be regurgitated into the

esophagus and into the mouth where it is re-chewed and re-swallowed ( helps break down this difficult to digest diet)

Allows “eructation” of built up carbon dioxide and methane gas in the rumen. Gasses are forced into the reticulum and up the esophagus

Interference with eructation leads to bloat which can be deadly

Fermentative digestion Begins in the rumen Bacterial, protozoal and a small amount

of fungi utilize their enzymes to begin breaking down food

The microbes utilize the energy in the diet to grow and reproduce

Carbohydrate metabolism Cellulase enzymes digest cellulose and

transform the complex carbohydrate into simple sugars

These simple sugars are not available to the host animal ( like they are in monogastric animals) instead they are absorbed and utilized by the microbes which produce Volatile Fatty Acids ( VFA’s)

The host animal utilizes the volatile fatty acids

Carbohydrate Metabolism Continued Volatile fatty acids are the byproducts of

anaerobic fermentation by microbes in rumen

Anaerobic fermentation means it does not utilize oxygen

Some of the VFA’s are utilized by the ruminant to produce glucose

Other VFA’s are used to produce adipose tissue and milk fat

Protein Metabolism Rumen microbes digest proteins just like

carbohydrates Proteases ( enzymes) reduce long

proteins to amino acids ( the building blocks of proteins) and short chain peptides ( short chains of amino acids)

Peptides are either incorporated into the protein structure of the microbes OR converted to ammonia ( NH3+) and VFA’s

Protein Metabolism Continued Liver secretes urea into the rumen, this

provides the rumen microbes with additional nitrogen ( the rest of the nitrogen they get from digesting the proteins in the diet)

Microbes get flushed from the reticolorumen to the omasum, abomasum and intestines where they serve as an additional protein source for the host animal

Urea is sometimes added to poor quality feeds to meet the nitrogen needs of the animal

Other rumen notes Microbes provide B vitamins, and

vitamin K The rumen environment is a delicate

balance of food, microbial growth and by-products

Abrupt changes in diet severely affect the production of methane, CO2, VFA’s and ammonia causing fermentation and changes in rumen ph

The Ruminant Stomach Omasum

Muscular organ located off the reticulum

Ingesta moves into omasum from reticulorumen

Prevents large particles from leaving rumen and entering abomasum

OMASUM

Source: University of California at Davis

head tail

Omasum primary functions Break down food particle further and move them

into the abomasum Absorb any excess VFA’s Remove bicarbonate ions from ingesta ( to avoid

altering acid ph of abomasum) Bicarbonate ions come from the saliva ( ruminants

produce a huge amount of saliva which goes into the rumen to help buffer ph)

If saliva flow is blocked by a foreign object or lack of production, the animal can become severely acidotic ( remember VFA are ACIDS)

The Ruminant Stomach Abomasum

“True stomach” of ruminant

Functions similar to

monogastric stomach

ABOMASUM

Source: University of California at Davis

head tail

Young Ruminant Digestive Tract Functions as a monogastric stomach No fermentative digestion ( rumen and

reticulum are non functional) Reticular groove or esophageal groove

forms when suckling and allows milk to go directly to omasum

Bucket fed calves don’t form this groove and milk spills into the rumen and reticulum

Young ruminant continued Abomasum is largest of 4 stomachs for

the first few weeks of life Rumen and reticulum development rate

depends on diet - grain and hay fed- develops at 3 weeks - milk fed develops at 3 months Veal calves are fed milk for their entire

short lives to produce a very tender soft meat,

Digestive System Chronology GI tract extends from mouth to the anus

and performs different functions at different sections

1. Prehension2. Mechanical grinding down of food3. Chemical digestion of food4. Absorption of nutrients and water5. Elimination of waste material

Prehension Grasping with teeth or lips Cows do not have upper incisors, they

have a toothless area called a dental pad

Cows use the bottom incisors and dental pad to bite grass

Dogs, cats have sharp tearing teeth to rip flesh

Mechanical grinding down of food Carnivores have pointed teeth to facilitate

holding and tearing of food Herbivores have flat surface molars that

grind from side to side to break down plant material

( watch a rabbit chew, horses, cattle chew the same way) horses form sharp edges ( points) on their

molars that have to be filed down from time to time ( floating the teeth)

Chronology of Digestion: Mechanical Grinding Down of Food

Carnivore TeethPointed to facilitate holding and tearing of food

© Clinical Textbook for Veterinary Technicians 6th ed.; McCurnin, Bassert

Chronology of Digestion: Mechanical Grinding Down of Food

Incisors – Teeth in the front for holding and tearing

Canines – Pointed teeth located at corners for tearing and shredding

Premolars – Located just before the molars and are used for grinding in all species

Molars – Used for grinding

Chronology of Digestion: Mechanical Grinding Down of Food

Herbivore TeethFlat, occlusal surface for grinding

Ruminant TeethNo upper incisors or upper canine teeth

Chronology of Digestion: Mechanical Grinding Down of Food

Dental Pad

Thickconnective

tissue

Diastema

Teeth terminology Maxilla – upper jaw Mandible- lower jaw Lingual- inner side of lower arcade of teeth

that face the tongue Labial- outer surface of upper and lower

arcade teeth that face the lips Palatal- inner side of upper arcade teeth that

face the palate Buccal- outer side of teeth on sides of mouth

that face the cheeks

Canine Triadan Numbering

Canine Dental Formula

Triadan

Feline Triadan Numbering

Feline Dental Formula

Triadan

Chemical digestion of food Saliva mixes with food during chewing Three pairs of salivary glands located

bilaterally ( one on each side) Parotid (2), mandibular(2), lingual (2) salivary

glands Saliva

1. moistens, softens, shapes and lubricates food

2. Aids in taste, acts as a buffer3. Provides digestive enzymes

Chemical Digestion of food continued Digestive enzymes and buffers in saliva1. amylase- in omnivore saliva, not

present in carnivores, breaks down amylase a sugar component of starch

2. Lipase- breaks down lipids3. Bicarbonate and phosphate buffers- in

cow saliva, neutralizes acids in rumen and maintain normal rumen ph ( up to 25-30 gallons of saliva a day)

Chemical Digestion of food continued Food moves from mouth to pharynx

where the epiglottis prevents food from entering the trachea

Food is transported into the esophagus Esophagus utilizes peristalsis, rhythmic

contractions to propel food to the stomach

Chemical digestion of food Stomach

1. Stores food2. Continues enzymatic breakdown of food

( pepsin, gastrin, mucus, hydrochloric acid all play a role)

3. Mechanical breakdown of food, mixing, grinding, contractions that move food

4. Ruminants have specific compartments with different functions ( rumen, reticulum, omasum, abomasum)

Chemical Digestion continued Liver- secretes bile acids to help with

digestion of fats, keeps the fats in solution

Pancreas- secretes enzymes into small intestine for breaking down nutrient

1. Protease for proteins2. Amylase for carbohydrates3. Lipase for fats/lipids4. Bicarbonate to neutralize stomach acid

Absorption of nutrients and water Small intestine consists of three parts,

duodenum, jejunum and ileum Continues peristalsis Villi and microvilli increase surface area

for absorption No clear demarcation between three

segments All 3 segments perform peristalsis,

absorb nutrients and water

Small Intestine Duodenum- first portion of the small

intestine receives contents of stomach Jejunum- majority of small intestine Ileum- where small intestine enters the

colon ( the cecum is located at this junction)

Cecum is very small in carnivores and large in herbivores like horses

Villi Villi-- millions of cylindrical fingerlike

projections from the intestinal wall- Provide large surface area for absorbing

nutrients- Crypts surround villi and replenish the

cells that cover the villi

Microvilli Microvilli- Brush border, extensions of the surface of the

cells that cover the villi- Increase the surface area of the cells and the

absorptive capacity- Contain digestive enzymes- Clinical example TGE transmissable gastroenteritis in pigs and parvovirus in dogs attack and destroy the villi preventing absorption of nutrients from the intestinal tract

Functions of Small Intestine Small intestine absorbs electrolytes

( Na, Cl, K, etc) water, and vitamins Absorbs carbohydrates, fats, proteins

after chemical digestion via enzymes

Nutrient digestion in the small intestine Carbohydrates- digested by amylase

secreted from the pancreas Proteins- digested by proteases secreted

by the pancreas Fats- digested by bile acids from liver

( helps emulsify fat ( keep in solution), further broken down by lipase secreted from pancreas

Elimination of Waste Material Large intestine: cecum and colon- Recover fluid and electrolytes- Store feces until elimination- Some microbial action- Differences between species dependent

on diet

Elimination of Waste material Carnivores- colon- simple, tubular, contracts to move

feces through- Cecum “ blind sac” poorly developed Herbivores- Colon – large bacterial population of

microbes for fermentation- Cecum “blind sac” more developed,

larger than carnivore

Colon Colon in carnivore is much smaller than

in herbivores Responsible for reabsorbing water and

electrolytes

Elimination of Waste in herbivores such as horses Colon and cecum comprise the “Hindgut” 4 sections, cecum, ventral colon, dorsal

colon, small colon More highly developed than small intestine Has greater capacity for fermentation Unique digestion path- colonic impaction is

most common form of colic in horses

Equine Digestive System

Rectum and Anus Rectum- Terminal portion of colon- Contains mucus secreting glands- Sensory receptors detect

stretching/distension and triggers defecation

Anus- Internal and external sphincters allow controlled passage of feces

Next Week… Session 2:

Basic Nutrients