Lecture 8 - diseases

Question 1

Malnutrition causes?

Answer 1

immunosuppression

- increases risk of infection

Question 2

What about horses magnifies problem feeding practices

Answer 2

small stomach capacity

tight sphincters

Question 3

Factors that compound nutrition related diseases

Answer 3

Stall confinement

increased housing density

Question 4

USA national health monitoring system report for 2000

Answer 4

• 13% of all horses (exlcuding racetracks) suffered from laminitis
• 4.7% had to be euthinized

Question 5

Laminitis

Answer 5

• 2nd most lethal condition of horses following colic
• lamellae of hooves weaken and inflammation sets in with onset foot pain
• lamellae normally support suspensory apparatus, which attaches to coffin bone
• lamellae separate from coffin bone inside hoof and the weight forces it down into the hoof capsule, can even perforate the sole
• disturbance in blood flow can change growth rate of hoof wall
• heel grows fast than toe, growth rings of hooves

Question 6

Hoof composition

Answer 6

distal phalanx (coffin or pedal bone)
lamellae
navicular bone
deep flexor tendon

Question 7

Acute vs Chronic Laminitis

Answer 7

Acute

• 24-72hrs
• shifting of weight from toes to heels

Chronic
-4 or 5 days +

Question 8

Determining whether chronic laminitis has occurred?

Answer 8

Growth rings on hooves

- the more space out the rings at the heal, more likely chronic

Question 9

Major cause of laminitis

Answer 9

Carbohydrates

• high intake of soluble from overgrazing of lush pasture
• overload of grain and forages
• excess undigested in SI and fermented in cecum and LI

Question 10

How laminitis develops - LI to stomach

Answer 10

Carbs fermented in cecum and LI

• large increase of lactic acid producing bacteria (anaerobic lactobacilli and streptococci)
• decreases intracecal pH from 7 to 4
• proliferation of starch fermenting organisms declines because of low pH
• lactic acid accumulation causes damage to intestinal mucosa
• increased permeability of intestinal epithelium to bacteria and endotoxins

Question 11

How Laminitis develops - intestinal bacteria

Answer 11

Increased permeability of intestinal epithelium

• intestinal bacteria produce metabolites that activate metalloproteinases in the hoof wall
• weekens bond between hoof wall and coffin bone

Question 12

How laminitis develops - endotoxins

Answer 12

endotoxemia - endotoxins from stomach reach blood

- reduces blood flow to the lamella of the hoof

Question 13

How laminitis develops - biogenic amines

Answer 13

Increase lactic acid in intestinal tract

• causes microbial breakdown of amino acids
• have hormone like properties including vasoconstrictor effects
• cause constriction of digital arteries and veins via stimulation of serotonergic receptors or displacement of norepinephrine from perivascular nerves

Question 14

Biogenic amines

Answer 14

serotonin
epinephrine
norepinephrine
putrescine
spermine
spermidine
histamine
tryamine

Question 15

Lactic acid producing bacteria

Answer 15

lactobacilli

streptococci

Question 16

First signs of laminitis

Answer 16

lameness and awkward stature

• from decreased blood flow
• caused by endotoxemia and biogenic amines

Question 17

Cool season grasses have high concentration of

Answer 17

fructan

• fructose rich polymers
• not degraded in small intestine
• higher risk of laminitis

Question 18

Cool season grass examples

Answer 18

perennial
rye
timothy 
brome
orchard grass
small grains - oats, wheat, barely

Question 19

warm season grass examples

Answer 19

bluestem
crabgrass
switchgrass
Bermuda grass

Question 20

soluble carbohydrate content of plants is affected by

Answer 20

plant species
season
time of day
weather and soil fertility

Question 21

Main risk factor of laminitis

- steps in preventing this

Answer 21

consumption of lush pasture

• monitor time on pasture
• fructan content in grass highest in spring and early summer
• fructan peaks during the day, so early morning and evening grazing is recommended
• stems are consumed with overgrazing, has highest fructan content
• laminitis complications minimized with mineral oil or activated charcoal
• early cut hay should not be avoided
• fall cold stress may cause premature hay, high fructan

Question 22

Non structural carbohydrates (NSC)

Answer 22

simple sugars, starch and fructans

Question 23

NSC recommendation

Answer 23

15% NSC to minimize laminitis risk

Question 24

Exertional Rhabdomyolysis caused by

Answer 24

results from skeletal muscle injury

- cell membrane ruptures, cell contents leak into blood

Question 25

Exertional Rhabdomyolysis characterized by

Answer 25

Elevated blood myoglobin, creatine kinase, aspertate aminotransferase and aspertate transaminase myoglobinuria - dark discolouration to urine (black water)

Question 26

Exertional Rhabdomyolysis other names

Answer 26

tying up azoturia black water monday morning disease

Question 27

Exertional Rhabdomyolysis first found

Answer 27

draft horses - work 6 days a week, rest on sunday - stiff hindquarters on monday morning after rest, difficulty rising - Monday Morning Disease

Question 28

Exertional Rhabdomyolysis symptoms

Answer 28

profuse sweating increased pulse and respiration rates discoloured urine (myoglobinuria)

Question 29

Exertional Rhabdomyolysis two subcategories

Answer 29

1. PSSM - Polysaccharide storage myopathy - mainly quarter horses, warm bloods and draft breeds - characterized by abnormal muscle glycogen metabolism 2. RER - Recurrent ER - thoroughbreds in training, Arabs and standardbreds - abnormal intercellular calcium metabolism in muscle and abnormal contraction of muscle fibers

Question 30

Exertional Rhabdomyolysis diagnosing

Answer 30

Blood CK levels - rise 2 - 12 hours following muscle injury - peak 1-3 days following injury - can reach 5x normal

Question 31

Cause of muscle stiffness in Exertional Rhabdomyolysis

Answer 31

Rapid calcium influx into muscle cells cause necrosis and muscle stiffness - theory

Question 32

Susceptibility to ER dependent on

Answer 32

``` age sex temperate exercise levels lameness - nervous animals higher risk ```

Question 33

Severe recurrent ER metabolite concentrations

Answer 33

low blood sodium, calcium and chloride elevated potassium and phosphorus - excess sweating and release of electrolytes from damages cells

Question 34

Specific dietary problem with ER and performance horses

Answer 34

energy dense diets are required for performance - but also promote ER - high fat low starch provide concentrated energy may benefit

Question 35

Race horses typical diet | - how to change diet

Answer 35

sweet feed - high starch feed - contains corn, oats, wheat meddling and molasses - most likely to cause ER introduction to a new diet could take up to 3 months - vegetable oil added to rice bran improve palatability

Question 36

Current thought on ER cause

Answer 36

abnormal calcium homeostasis in skeletal muscle - cramps caused because calcium not released to cells - VitE and selenium no benefit