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183 Cards in this Set

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  • Back
Horses are ________ fermentors. That means the fermentation system is _______ the gut or stomach.
Hindgut, behind
What are the four parts of the Hindgut?
1) Cecum
2) Large Colon (Ascending Colon)
3) Small Colon (Descending Colon)
4) Rectum
Does extensive fermentation occur before or after primary sites of digestion and absorption?
AFTER
What are the two parts of the stomach?
Squamous portion (upper)

and

Non-squamous glandular portion (lower)
How long is the Jejenum?
60-65ft
How often does a horse empty its stomach normally?
About 2 - 12 hours
How long does it take for food to pass from the stomach to the cecum?
About 4 hours
What is the purpose of the Ileum?
To push food into the cecum
What is a big characteristic of the Illeum?
Illiocecal Band continuous with the dorsal cecum band
What are the 3 parts of the cecum? Where does it sit?
1) Base attaches to the body wall

2) Apex runs along the ventrum toward the sternum

3) Body
Where does ingesta flow from out of the cecum into?
Flows out of the cecum into the RIGHT VENTRAL COLON (cranially)
Where does the ingesta flow from out of the Right Ventral Colon into?
Through the sternal flexure then into the Left Ventral Colon (caudally)
What separates the two ventral colons?
The sternal flexure
Where does the ingesta flow from out of the Left Ventral Colon?
Uphill out around the pelvic flexure
What are the common sites for constipation pluggage in horses? Why?
1) The pelvic flexure
2) The Transverse Colon

there is a narrowing there
How can you tell the dorsal colon from the ventral colon
The ventral colons have sacculations
Where does ingesta flow to when it leaves the pelvic flexure?
Into the Left Dorsal Colon (Cranially)
Where does ingesta flow to when it leaves the Left Dorsal Colon?
Into the Right Dorsal Colon (Caudally)
Where does the Right Dorsal Colon lead into?
Transverse Colon
Where is fecal ball made?
The descending colon (small colon) about 12ft
What is the band of the descending colon?
An inch and a half wide band off the serosa surface of the descending colon.
Where does the descending colon lead into and the fecal balls go into?
Rectum
What fibrous feeds are digestible by horses hidgut formentation?
Cellulose and Hemicellulose are digestible

Lignin is absolutely not digestible
Where is water primarily absorbed in the horse?
The Ascending Colon
What is another name for Large Colon?
Ascending Colon
What is another name for Small Colon?
Descending Colon
What is the complete order of where ingesta goes beginning from the cecum?
1) Cecum
2) Right Ventral Colon
3) Sternal Flexure
4) Left Ventral Colon
5) Pelvic Flexure (plug point)
6) Left Dorsal Colon
7) Diaphragmatic Flexure
8) Right Dorsal Colon
9) Transverse Colon
10) Rectum
What are the 4 parts of the oral cavity and their functions?
1) Lips - Prehensile lips that bring food tot he mouth. Also form suction to drink. (CN VII)

2) Tongue - propulsion of feed bolus to pharynx to be swallowed (CN XII)

3) Teeth - mastication, lateral excursion which increases the surface area of chewing, allows enzymes to begin digestion

4) Salivary Glands - Parotid, submaxillary, sublingual (moisten, lubrication, initiate digestion (amylase), buffers stomach acid (bicarbonate)
How many times does a horse chew a day?
About 60,000 times a day
What kind of teeth do horses have? What are special about them?
Hypsodont Teeth. They are Continually growing
What is the volum if saliva in horses a day?
40L a day
What factors affect the flow of saliva in horses?
Parasympathetic and sympathetic tone.

Also type of feed
What is another name for swallowing?
Deglutition
How does food travel down the esophagus?
Through peristaltic contractions
Can a horse vomit?
No, they would rupture their stomachs before they vomit
What is secreted in the stomach and what type of cells secrete them?
HCl - Parietal Cells

Gastrin - G-Cells

Pepsinogen - Chief Cells
What is the Margo Plicatus?
The margin that separates the squamous portion of the stomach from the glandular portion of the stomach
Where do ruptures usually occur in the stomach?
The greater curvature
What is the importance of the feed bolus?
Prevents gastric acid from splashing back up to the squamous portion
How does the glandular portion help protect the stomach?
- Mucus Barrier
- Bicarbonate Secretion
- Rapid regeneration and repair
- Reflux of duodenal secretions neutralizes HCl (pancreas/hepatocytes)
How long are the small intestines?
About 70 feet long
How much fluid is usually in the small intestine
40-50L
What is the transit time of food through the Small Intestine?
3-4 Hours
What is the primary site of digestion and absorption of proteins, fats, carbohydrates, and vitamins and minerals?
The Small Intestine
What is a main cause colic?
Large meals promote rapid transit to the cecum.

Leads to incomplete pre-cecal digestion
What is the volume of liquid in the cecum?
30L
What is found in the cecum that is important for digestion?
Bacteria, Fungus, Microflora
What do the microbes produce as their by products?
VFA, Gas, B-Vitamins and Vitamin K
What are the advantages and disadvantages to horses utilization of cellulose?
Adv.
- Ultra abundant in the environment
- Easily obtained
- Plant cell walls fiber high in energy

Dis.
- indigestible by ammalian digestive enzyme
- Cellulase is found only in bacteria and some protozoans
Where is most of the water absorbed in the horse's digestive tract?
In the "Ascending Colon" or large colon
What is the digestive function of the transverse colon?
No real digestive responsibilities

But it is the area of narrowing that can cause blockage
Where is feces stored and expelled from?
The Rectum
What is the function of the small colon?
The small colon (descending colon) - creates fecal balls (aka road apples)
Where are VFA's produced? Where are they absorbed?
Produced in the cecum/large colon absorbed directly into the blood stream.
What are the 3 VFA's that are produced?
1) Acetate - provides immediate energy for muscle cells
- decrease acetate with increase grain fed (decrease forage)

2) Proprionate - gluconeogenesis in the liver, Increase proprionate with increase in grain
- can provide significant source of glucose

- Butyrate
Describe the absorption of VFA's
Across the large intestinal wall through passive difussion down pH gradiant as free acids

- Directly into the portal blood - travels to liver/muscle
What is the rate of absorption related to molecular weight of VFA's
Acetate > proprionate > butyrate
Where does digestion of Non-structural carbohydrates begin?
In the Stomach ---> SI

50 - 70% total NSC digestion in SI
What are the enzymes released from teh pancrease via common bile duct into the duodenum?
1) Amylase
2) Sucrase
3) Lactase
What enzyme is primarily responsible for starch digestion in horses?
Amylase
Where does non-digested starch go?
They go into the hindgut and the cecum receives undigested starch
What is a well known cause of colic in horses today?
Non-Structural Carbohydrates

(Incomplete Pre-cecal Digestion)
How do concentrates lead to colic?
Excess starch by-passes SI digestion --> cecum

Specialized microbes in cecum and colon produce lactic acid and alters pH,

Injures mucosa - -> dysmotility

Normal Microbe population dies
- Endotoxic shock -- Laminitis
- Gas Production
How do we improve pre-cecal digestion?
1) Feed NSC separately from forage

2) Consider source of starch

3) Decrease amount of starch intake / meal/ day

4) Processing of startches
-Oats are highly digestible
What are some cases in which NSC should be avoided? (excess starches)
1) Cushings Syndrome

2) Equine Metabolic Syndrome

3) Laminitis

4) Obsese
What are some structural carbohydrates?
Roughages - low starch
- High fiber
- Low Digestible energy
What are some non-structural carbohydrates?
Grains
- High Starch
- Low Fiber
- High Digestible Energy
What is glycemic index?
Measure of effects of CHO on blood glucose
Characteristics of High Glycemic Feeds? and examples
CHO break down quickly during digestion, releasing glucose rapidly into circulation

Ex. Corn and oats
Characteristics of Low Glycemic Feeds? and examples
CHO break down more slowly,releasing glucose more gradually into the blood stream

ex. corn oil, alalfa, roughage
What is one of the most common ways to feed fat in horses?
Corn Oil
What is normal glucose level in horses?
80-120
What is the path of ingest of food beginning at the oral cavity and ending at the cecum?
1) Oral cavity
2) Esophagus
3) Pylorus of Stomach
4) Duodenum
5) Jejenum
6) Ileum
7) Cecum
What is the initial site of fermantation in the horse?
The Cecum (analagous with human appendix)
What is another name for the sacculations on the Right and Left ventral colons?
Taenia or Haustra
What is the foregut comprised of?
Small Intestines and StomachW
What is the purpose of the foregut?
Responsible for digestion and absorption of most all non fibrous feeds that are ingested. (protein, fat, nsc like sugar and starch)
Where does nutrient digestion begin?
In the oral cavity
What type of motion do horses chew with?
Lateral Excursion
What is special about hypsodont teeth?
They are constantly growing
What is the bar of the mouth in horses?
The area devoid of cheek teeth where the bridle or bit rests in the horse's mouth
What are "fighting teeth" in horses?
Canines and not usually seen in females
What are cheek teeth?
Premolars and Molars they are used for grinding feed in preparation for the digestive process
How many of each teeth are there in a horse?
4 Canines (Males)

6 Premolars Upper, Premolars Lower

6 Molars Upper, 6 Molars Lower

6 Upper and Lower Incisors as well
What does "floating" the teeth refer to?
A routine dental care procedure in horses
What are the three pairs of salivary glands in horses?
1) Parotid
2) Submaxillary
3) Sublingual
How much saliva can a horse produce a day?
40 liters or 10 gallons
What is deglutition? Where does it begin?
The act of swallowing, it begins in the pharynx moving the feed bolus into the esophagus via peristaltic activity
What forms the upper esophageal sphincter?
The cricopharyngeus muscle attached to the cricoid cartilage
What are two factors that prevent regurgitation in horses?
1) Esophagus enters the stomach at an oblique angle

2) The tone of the musculature of the lower esophageal
What are the two factors that gastric emptying depend on?
1) Volume within the stomach

2) Rate of SI digestion
What are parietal cells in the glandular portion of the stomach responsible for?
Secreting HCl into the gastric lumen
What are the 3 receptors on the parietal cell that must be bound concurrently?
1) Gastrin
2) Acetylcholine
3) Histamine 2
What do the G-cells in the stomach, duodenum, and pancrease secrete?
Gastrin
What do chief cells secrete? What is its function?
Pepsinogen (precursor of pepsin)

Pepsin is an enyzme responsible for demolition of proteins into amino acids for absorption within the SI tract.
What is the cardiac region of the stomach?
The cardiac region (the area of entry of esophagus into the stomach)
What surrounds the area from the cardia to the margo plicatus?
Esophageal squamous mucosa
What is the margo plicatus?
It denotes the line of demarcation between the gastric squamous mucosa from the glandular mucosa of the stomach
What does the lesser curvature of the stomach separate?
The cardiac and pyloric regions of the stomach
What is the significance of the greater curvature of the stomach?
It is the area of the stomach in which greatest tension occurs with gastric distention
Why are horses that are meal fed more prone to acid injury and formation of gastric ulcers?
Because they have difficulty maintaining the feed bolus
The transit of ingesta through the SI tract is relatively rapid/slow?
Rapid with most feeds reaching the large intestines within 3-4 hours
Where does the common bile duct empty to in horses?
Empties into the proximal duodenum
What is the purpose of the gall bladder and why do horses not have one?
The gall bladder is storage for digestive enzymes that are released during meal time

They are not in horses because horses were intended to have continuous, small, frequent meals
Since horses do not have a gall bladder, when are digestive enzymes released from the pancreas and liver?
They are continuously being released throughout the day
Which tract is the primary site for digestion and absorption of protein, fat, NSC, vitamins, and minerals?
The small intestinal tract
What is the limited digestive capacity of starch based on in the horse digestive tract?
Insufficient supply of amylase from pancreas
Why does incomplete pre-cecal digestion of starch cause colic in horses?
The excess starch that is incompletely digested enters the cecum and causes overgrowth of certain populations of bacterial microbes
Where is the initial site of fermentation of forage feeds and what is its rate of passage?
The initial site is the cecum and the rate of passage is relatively slow (9 hours) compared to SI tract (3-4 hours).
What percent of forage feed to NSC (sugars) should be fed to the horse to maintain the microbial population within the cecum and colon?
More than 50% fiber from forage feeds and very low amounts of NSC
What is the primary site of water absorption in horses?
The ascending colon (large colon)
What is the only part of the plant that remains 100% undigestible?
Lignin
Horses release gas from the _______ and cows release gas from the __________
Horse - Rectum

Cow - Oral (eructation)
What are the digestive responsibilities of the transverse colon?
It has none
What is the final site of water re-absorption as well as creation of equine fecal ball (road apple)?
The descending colon (small colon)
What is the storage receptacle for feces until contraction initiates bowel movement?
The Rectum
What is the daily fluid requirement for a normal horse with no forced exercise (maintenance fluid)?
50ml/kg/day
What is maintenance fluid?
The amount of water required to replace insensible losses of body water that occur over the course of a day
Where does the horse get its water from if it is fed on a typical hay and grain diet?
90% of its water is from periprandial drinking
What are the sites of water absorption in the horse?
cecum, ascending colon (large colon), and the final site descending colon (small colon)
How can a horse owner increase their horses water consumption?
1) provide additional water sources which contain electrolytes

2) Offering warm water during winter months
What is digestible energy and what is it measured in?
The amount of energy available to the horse in digestible form.

Measured in calories
What are structural carbohydrates and what are nonstructural carbohydrates?
Structural - Forage Feeds

NSC - Sugars/ starch
Cecal and colonic microflora produce which enzyme capable of hydrolyzing forage feeds?
Cellulase
What are the benefits of feeding long stem forages?
1) Increase particle size
2) Slow passage rate of digesta
3) Increase water intake
4) Reduces tail chewing, wood chewing, and eating excrement
Does fermentation occur in the small intestine?
Yes in the distal portion
What is the optimal pH for microbes in the cecum and colon?
pH = 6.5
How long is the entire process of fermentation (all of large intestine)
24-36 hours
Increasing amount of grain fed or decreasing forage fed percentage will decrease production of which VFA?
Decrease Acetate
Which VFA contributes most to liver and muscle glycogen storage?
Proprionate
Which VFA is most intensely used by muscle tissue for energy?
Acetate
VFA absorption occurs across the large intestine via what process?
passive diffusion down the transmucosal ph gradient
What accompanies VFA's when they are absorbed in the large intestine?
Sodium, Chloride, and for every 1 mol of VFA there is 1 mol of water
What is the only form of NSC that can be directly absorbed from the SI?
Monosaccharides
What is the byproduct of the microbes in the SI digestion? (Bacillus, Lactobacillus, and Streptococcus)
Lactic acid
Explain how excess NSC causes colic
Too much NSC --> SI microbes grow --> produce lactic acid --> kills off other microbes --> bacterial endotoxins released and absorbed into blood
What are some sources of NSC? Which one is better and which ones are worse?
Oats (most digestible form of starch)

Molasses low digestibility like corn but improves palatability

Corn low digestibility high in energy low in protein
What amount of starch / kg of body weight should not be exceeded to reduce risk of colic associated with NSC ingestion?
Should not exceed 2 grams / kg body weight
What are some ways to increase NSC digestibility?
1) Consider source and digestibility

2) Consider amount of NSC offered daily

3) Processing such as fine grinding to less then 2m

4) Cooking

5) Individual horses digestibility should be considered
Which horses should are more prone to excess NSC?
Cushings Syndrome, Equine Metabolic Syndrome, Laminitis, or Obesity
Which horses require as much as 35% of their diet from NSC?
Racehorses or high performance horses

Lactating Mares

Underweight Horses (hard keepers)
What type of carbohydrates have a low and high glycemic index?
High Glycemic Index - Carbohydrates that break down and release glucose quickly

Low Glycemic Index - Carbohydrates that break down and release glucose more slowly
What is the minimum percent fat in a typical forage-based diet?
2-3%
What is enterohaptic recirculation?
90% of bile acids are recycled daily when they are absorbed from the ileum and transported to the liver
What happens to excess lipids?
1) processed to VLDL adipose storage

2) Some become ketone bodies
What is hyperlipidemia?
Excess circulating triglycerides in bloodstream (greater than 500mg/dl), and milky colored serum
What are some important essential fatty acids (parent compounds of)
Omega 6 - Linoleic acid

Omega 3 - Linolenic Acid
How does addition of fat into feed help?
Digestible energy is increased without increasing the starch content of feed
What is the typical make up of protein in diet?
7-20% with foals and lactating mares having the greatest protein requirements
Which essential amino acid is required for growth of young horses and is considered the first limiting amino acid for growth?
Lysine
As crude protein in dry matter increases, digestibility increases or decreases?
Increases
What are some high quality protein sources in horses?
1) Legume Hay (alfalfa)
2) Soybeans
3) Rice Bran
4) Oats and Seeds (linseed oil)
Are horses able to utilize non-protein nitrogen sources?
No, therefore feeds with protein level based on urea will not accurately reflect protein availitbilty
Why should high protein rations be used with caution in hot weather?
More body heat when breaking down protein.

Can be reduced by adding 10% fat to diet which reduces heat load by 5%
Which fat soluble vitamins can the horse produce on its own and which ones must be ingested?
Produced on own - DK

Ingested - AE
What is the other name for Vitamin A and what is it important in?
Also known as retinal

Important in vision especially at night

Also important in bone, muscle growth of young horses, reproduction, and healthy skin
Deficiency in Vitamin A causes?
1) Depressed Appetite
2) Weight Loss
3) Dull Haircoat
4) NIght Blindness
5) Epiphora (Tearing)
6) Anemia and Seizures
How long does Vitamin A last in the body?
Up to 6 months
What is Vitamin D important for?
Calcium and phosphorus balance

Increases absorption of Calcium and phosphorus from SI Tract
When does Vitamin D need to be supplemented?
When horses do not receive fresh forage or access to sunlight
Vitamin D deficiency causes?
Rickets in young animals but has not be observed in horses
What is the other name for Vitamin E?
Alpha Tocopherol
What is Vitamin E important for?
1) Antioxidant of neurons and cells

2) Enhances immune function, DNA synthesis

3) Assist in absorption and storage of Vitamin A
Vitamin E deficiency causes?
1) White muscle disease also linked with selenium deficiency

2) Equine motor neuron disease (muscle wasting and recumbency)
Vitamin K is important for?
Coagulation Factors and provides support for bone metabolism and vascular health
Vitamin B1 is also known as?
Thiamine
Vitamin B1 is important for?
neuronal health, nerve transmission, and CHO metabolism
Brakenfern toxicity is most common cause of which Vitamin deficiency?
B1 (thiamin)
Vitamin B2 is also known as?
Ribovflavin
Vitamin B2 is important in?
ATP Synthesis
Vitamin B12 is also known as?
Colbalamin and is commonly grouped with folic acid
Vitamin B12 is important for?
Synthesis of red blood cells
Vitamin B12 deficiency will cause?
Anemia
What is important about Vitamin B12?
Produced from micro-organisms therefore commonly supplemented in performance horses
Vitamin C is also known as?
Ascorbic Acid
Vitamin C is important in?
Antioxidation

Formation of Bones and Teeth

Utilization of B- Vitamins, cholesterol, glucose, and improves absorption of Iron
Where is Vitamin C produced?
Liver from glucose
What are the macrominerals?
1) Calcium
2) Sodium
3) Phosphorus
4) Potassium
5) Chloride
6) Sulfur
What are the microminerals?
1) Copper
2) Zinc
3) Iodine
4) Iron
5) Manganese
6) Selenium
Excess calcium absorbed from the GI tract is?
Secreted into making calcium carbonate crystals (normal)
Excess of which mineral will cause Big Head disease or Bran disease in horses?
Phosophorus
What is the normal ratio of Calcium and Phosphorus in horses? Why is it important?
1.43:1

Important because Ca and P compete directly for absorption in SI prevents mobilization of bone
What is ratio for Ca and P in growing horses?
1.5:1

Never Exceed 3:1