countermeasures for equine laminitis (mc intosh)
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TRANSCRIPT
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COUNTERMEASURES FOR EQUINE LAMINITIS
Dr. Bridgett McIntoshUniversity of Tennessee
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Meet our presenter:
Dr. Bridgett McIntoshUniversity of Tennessee
Dr. Tania CubittPerformance Horse NutritionQuestion facilitator:
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Topics of Discussion• Laminitis & hoof anatomy• Dietary causes of laminitis • Risk factors for laminitis in horses• Risk factors in forages and feeds • Current research on pasture associated laminitis• Countermeasures for avoidance of laminitis
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• Systemic inflammatory disease• Manifests itself in the hoof• Inflammation and degeneration
of the soft tissue which connects the hoof wall and the coffin bone (lamina)
What is Laminitis?
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What is Founder?• A change in the position of the coffin
bone in the foot due to laminitis.• “Chronic laminitis” with rotation of the
coffin bone within the hoof.• Lameness due to malposition of the
coffin bone within the foot.
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Hoof Anatomy
http://www.uoguelph.ca (Gunn, 2009)
Coffin bone also called “Pedal Bone” or “P3”
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Cross section of the equine hoof
•Lamina (L)
•Coronary Band (C)
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Anatomy of Lamina• Epidermal & Dermal• Primary and Secondary
– Form strong attachment to connect coffin bone to hoof wall
Pollitt, 1998
• Basement Membrane– Nutrient exchange
between tissues
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Coffin Bone Rotation• Degeneration of lamina.• Due to the design of the
coffin joint the coffin bone rotates towards the ground.
• The separation between the hoof and bone is greatest at the toe
White, 2005
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Causes of Laminitis Grain Overload(7.4%)
Lush Pasture(45.6)
Unknown(15.4%)
Other known(26.9%)
Colic/Diarrhea(2.7%)
RetainedPlacenta (2.1%)
USDA- NAHMS, 2000
OVER 50%
DIETARY CAUSES
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Basics of Equine Nutrition• Horses are non-ruminant
herbivores• Forage is primary
component of diet• Digestive system designed
to utilize fiber from forage via microbial fermentation in hindgut
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• Small, frequent meals– Graze approximately 14
to 18 hours per day – Cover distances of up to
20 km/d • Ability to digest large
amounts of forage and feed at once is limited
Feeding Behavior
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Glucose
Insulin
(Rodiek et al., 1991)Slide modified from Kibby Treiber
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Glucose
Insulin
(Clarke et al., 1990; Valentine et al., 2001)Slide modified from Kibby Treiber
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Hindgut pH
Gram negative bacteria killed off
Gram positive lactate producing bacteria
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Damage to cecum from high doses of starch
Kreuger et al., 1986
LAMINITIS!NORMAL
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ANIMAL FACTORSObesityInsulin resistanceMetabolic syndrome”
DIETARY FACTORSNonstructural Carbs
- Pasture Conditions- Harvest Conditions
- Feed Ingredients
RISK FACTORS FOR RISK FACTORS FOR LAMINITISLAMINITIS
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Obesity• Body Condition Score 8 to 9• Too many calories• Not enough exercise• Thrifty genotypes• Prolonged obesity• No seasonal shift in energy balance• Often encouraged in the show ring
Risk Factors in Horses
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Obesity/Regional Adiposity
Risk Factors in Horses
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Insulin• INSULIN is a regulatory hormone for metabolism,
vascular function, inflammation, tissue remodeling, and growth– Secreted by pancreas to move glucose into tissues
• INSULIN RESISTANCE is failure of tissues to respond appropriately to insulin (decreased insulin sensitivity) – Insulin Resistance decreases glucose uptake by tissues – Laminitis- affects tissues of hoof (lamina)
Risk Factors in Horses
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Insulin Resistance (IR)• Sugar & Starch in forage/feed = blood glucose• Insulin secreted in response to glucose• IR = high blood insulin levels
– Insulin = vasoconstrictor– Vasocontriction decreases blood supply to hoof– Thus decreasing nutrients
Risk Factors in Horses
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Equine Metabolic Syndrome• Characterized by:
– Obesity/Regional Adiposity
– Insulin Resistance– Laminitis
Risk Factors in Horses
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Pasture, Hay, Feed Ingredients• Nonstructural carbohydrates (NSC)
–Starch–Sugar–Fructan
Dietary Risk Factors
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Plant Carbohydrates
Cell contents Cell wall
FructanFructose StarchSucrose Hemicellulose Cellulose
Rapidly Fermented (Hindgut)
Glucose
Hydrolyzed (small Intestine)
Slowly Fermentable (Hindgut)
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• Starches– Cereal Grains– Legumes
• Sugars and Fructan– Cool Season Grasses
Dietary Risk Factors
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• Starch– Enzymatic >>>> glucose
• ESC (ethanol soluble carbs) >>>> glucose, fructose, sucrose • WSC (water soluble CHO) >>>> ESC + Fructan• NSC (nonstructural CHO) >>>> Starch + WSC• Fructan (not available commercially)
– Enzymatic >>>> fructose (glucose)
NSC Analysis
There are differences in nomenclature and techniques between laboratories
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• Series of trials to examine diurnal and seasonal variation in pasture NSC and physiological and metabolic affects on the grazing horse
• Virginia Tech, MARE Center
A Research Study on Equine LaminitisCurrent Research
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Five 42 hour trials
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Nutrient April May August October January Hay
%CP 21.3 ± 1.4a 14.0 ± 0.2b 12.7 ± 0.2c 12.9 ± 0.2c 14.2 ± 0.3b 11.3 ± 0.5
%ADF 25.4 ± 0.2a 35.3 ± 0.2b 36.9 ± 0.5b 37.9 ± 0.2b 39.1 ± 0.3b 41.7 ± 0.4
%NDF 46.4 ± 0.3a 64.2 ± 0.3b 64.0 ± 0.7b 66.2 ± 0.4b 66.5 ± 0.5b 62.1 ± 1.3
%NSC 20.3 ± 0.4a 11.7 ± 0.4b 9.2 ± 0.5c 6.9 ± 0.2c 7.1 ± 0.2c 8.9 ± 0.1
% Sugar 18.9 ± 0.4a 10.2 ± 0.4b 7.6 ± 0.5c 5.7 ± 0.2c 6.1 ± 0.2c 6.1 ± 0.1
%Starch 1.4 ± 0.04 1.5 ± 0.06 1.5 ± 0.06 1.1 ± 0.05 1.0 ± 0.03 2.8 ± 0.1
% Fat 4.0 ± 0.4a 2.8 ± 0.04b 4.3 ± 0.1a 3.8 ± 0.06a 2.2 ± 0.09b 1.6 ± 0.3
DE, Mcal/kg 2.8 ± 0.01a 2.2 ± 0.01b 2.1 ± 0.01b 2.1 ± 0.01b 2.1 ± 0.01b 1.9 ± 0.02
Nutrient content of forage
a,b,cFeeds differ between months (P < 0.05)
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April May
Circadian variation: NSC
0600 1800 0600 180002468
1012141618202224262830
R2 = 0.64,P < 0.01
Time
NS
C, %
0600 1800 0600 180002468
1012141618202224262830
R2 = 0.71P < 0.01
Time
NS
C, %
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0600 1800 0600 180002468
1012141618202224262830
Time
No
nstr
uctu
ral
carb
oh
yd
rate
(NS
C),
%
0600 1800 0600 180002468
1012141618202224262830
Time
No
nst
ruct
ura
l ca
rbo
hyd
rate
(NS
C),
%
0600 1800 0600 180002468
1012141618202224262830
R2 = 0.41P = 0.01
Time
No
nst
ruct
ura
l ca
rbo
hyd
rate
(NS
C),
%
AugustAugust
OctoberOctober JanuaryJanuary
October and January: Cloudy & Raining
August: Hot & Humid
LAB 1 PROCEDURE
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APRIL
0600 1800 0600 180002468
10121416182022242628
Sugar
FructanStarch
NSC
Sample h
% D
M
NSC Pasture Profiles
Thanks to our sponsor:LAB 2 PROCEDURE
MAY
0600 1800 0600 180002468
10121416182022242628
SugarFructanStarch
NSC
Sample h
% D
M
NSC Pasture Profiles
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AUGUST
LAB 2 PROCEDURE
0600 1800 0600 180002468
10121416182022242628
SugarFructanStarch
NSC
Sample h
% D
MNSC Pasture Profiles
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JANUARY
LAB 2 PROCEDURE
0600 1800 0600 180002468
10121416182022242628
Sugar
FructanStarch
NSC
Sample h
% D
MNSC Pasture Profiles
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0 10 20 30 40151617181920212223242526
2.0
4.5
7.0
9.5
12.0
14.5
17.0April
NSC Temperaturer = 0.72P < 0.001
Time, h
NS
C, %
DM
Am
bie
nt te
mp
era
ture
,°C
0 10 20 30 406789
10111213141516
891011121314151617May
r = 0.40P < 0.0001
Time, h
NS
C, %
DM
Am
bie
nt te
mp
era
ture
,°C
0 10 20 30 4013579
111315
161820222426283032
August r = 0.38P < 0.0001
Time, h
NS
C, %
DM
Am
bie
nt te
mp
era
ture
,°C
0 10 20 30 403456789
1011
67891011121314
October r = 0.72P < 0.0001
Time, h
NS
C, %
DM
Am
bie
nt te
mp
era
ture
,°C
0 10 20 30 404
5
6
7
8
9
10
23456789
January r = 0.29P < 0.0001
Time, h
NS
C, %
DM
Am
bie
nt te
mp
era
ture
,°C
There was a relationship between temperature and pasture NSC
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0 10 20 30 40151617181920212223242526
0
200
400
600
800
1000
1200AprilNSC Radiation
r = 0.62P < 0.001
Time, h
NS
C, %
DM
So
lar ra
dia
tion
, watts
/m2 0 10 20 30 40
6789
10111213141516
0
200
400
600
800
1000
1200May r = 0.42
P < 0.0001
Time, h
NS
C, %
DM
So
lar ra
dia
tion
,,watts
/m2
0 10 20 30 4013579
111315
0
200
400
600
800
1000August r = 0.47
P < 0.0001
Time, h
NS
C, %
DM
So
lar ra
dia
tion
, watts
/m2
0 10 20 30 403456789
1011
0
100
200
300
400October r = 0.58
P < 0.0001
Time, hN
SC
, %
DM
So
lar ra
dia
tion
, wa
tts/m
2
0 10 20 30 404
5
6
7
8
9
10
0
100
200
300
400
500January r = 0.34
P < 0.0001
Time, h
NS
C, %
DM
So
lar ra
dia
tion
, watts
/m2
Solar Radiation (Sunlight) also affected NSC concentration in pasture
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0 10 20 30 40151617181920212223242526
2025303540455055606570April
RHNSC r = -0.75P < 0.0001
Time, h
NS
C, %
DM
Rela
tive h
um
idity
, %
0 10 20 30 406789
10111213141516
40
50
60
70
80May r = -0.32P < 0.002
Time, h
NS
C, %
DM
Rela
tive h
um
idity
, %
0 10 20 30 4013579
111315
405060708090100110
August r = -0.59P < 0.0001
Time, h
NS
C, %
DM
Rela
tive h
um
idity
, %
0 10 20 30 403456789
1011
60
70
80
90
100
110October r = -0.84
P < 0.001
Time, h
NS
C, %
DM
Rela
tive h
um
idity
, %
0 10 20 30 404
5
6
7
8
9
10
60
70
80
90
100
110January r = -0.34P < 0.0001
Time, h
NS
C, %
DM
Rela
tive h
um
idity
, %
As humidity increased, NSC decreased in the pasture
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Environment influences pasture NSC concentration
• Most of NSC is sugars• Little variation in starch or
fructan (which were low)• Diurnal variation in April,
May, August in NSC • NSC levels related to
environmental factorsHow does pasture NSC
affect horses …
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Insulin was higher in grazing horses in AprilIn April, insulin was high in general
0
25
50
75
100
125GrazingControl
Time
Ins
ulin
, uIU
/mL
0
25
50
75
100
125GrazingControl
Time
Insu
lin, u
IU/m
L
APRIL MAY
Insulin
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09
30
12
30
15
30
18
30
21
30
00
30
03
30
06
30
09
30
13
30
17
30
21
300
25
50
75
100
125 Grazing
Control
Time
Insu
lin
, u
IU/m
L
09
30
12
30
15
30
18
30
21
30
00
30
03
30
06
30
09
30
13
30
17
30
17
30
21
300
25
50
75
100
125 GrazingControl
Time
Insu
lin
, u
IU/m
L
09
30
12
30
15
30
18
30
21
30
00
30
03
30
06
30
09
30
13
30
17
30
21
300
25
50
75
100
125Grazing
Control
Time
Insu
lin
, u
IU/m
L
August October
January
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Evident relationship in April
NSC (r2 = 0.507, P < 0.001) Insulin (r2 = 0.121, P < 0.001) Similar frequency (P = 0.36)
0
10
20
30
40
50
60
70
80
90
100
110
120
NSCInsulin-GrazingInsulin-Control
151617181920212223242526272829
0600 2400 1800
2130 Last blood sample
0930First blood sample
INSULINDAY 1-2
NSCDAY 1-2
0600
TIME
2400 1800
First pasture sample Last pasture sample
24001200 1800 0600 1200 1200 1800 0600 1200 2400 0600
Insu
lin
, m
IU/L
Fo
rage N
SC
, %D
M
Hay
As pasture NSC fluctuated throughout the day, insulin followed the same pattern in grazing horses. When pasture NSC increased, insulin increased 15 minutes later.
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Higher fecal lactate suggests rapid fermentation of sugars in grazing horses
Pasture Hay0.00.51.01.52.02.53.03.54.04.55.05.5 P = 0.007
Diet
Fec
al L
-lac
tic
acid
,m
mo
l/L
Grazing Control0.00.51.01.52.02.53.03.54.04.55.05.5 P = 0.04
Diet
Fecal
D-l
acti
c a
cid
,m
mo
l/L
Lactate- April
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• Fecal pH was slightly lower in grazing horses– Graze pH 6.9 (red)– Control pH 7.4 (orange)
GrazingControl0
1
2
3
4
5
6
7
8 P = 0.0008
Dietp
H
Fecal pH- April
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Research Conclusions• Circadian and seasonal variation
in insulin in grazing horses• Insulin associated with forage
NSC content • Digestive factors suggested
increased rapid fermentation• Define grazing management
strategies for avoidance of risk factors in horses and forages
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Implications of this Research
• Increased risk of laminitis via exacerbation of insulin resistance and rapid fermentation in the hindgut
• Avoid pasture laminitis through grazing management• More research needed in different regions, other forage
species, different breeds, etc…
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Other Considerations• Not all horses are at risk
– Genetics (“Thrifty Genotype” or “Easy Keeper”)
– Environmental Conditions– Feeding Management
• Hay and feed should be selected to reduce risks
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Hay & Pasture NSC
Forage TypeNSC
(% DM)Low NCS (%DM)
High NSC (%DM)
Grass Hay 13.1 8.2 18.0MMG Hay 12.5 8.4 16.7Legume Hay 11.1 8.8 13.4MML Hay 11.2 8.4 13.9Grass Pasture 12.8 7.1 18.0MMG Pasture 12.8 8.0 17.6
www.equianalytical.com2000-2006, 4,000+ samples
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Hay Production • NSC content reflects
amount when it was cut• Cut in AM = lower• Forages respire & lose
sugars after cut until moisture is < 40%– Fast dry, sunny = high NSC– Slow dry, humid = low NSC
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Reducing NSC in Hay
• Soaking– Sugars and fructans are water
soluble– Soak = lower NSC– Be aware of nutrient loss (???)– 30 min hot water– 60 min cold water– Poor out water
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What are low NSC Feeds?
Company Feed Name Protein Fat Fiber NSC
TN Farmers Co-op Equilite 1300 13 3 20 16
Blue Seal Carb Gaurd 12 8 25 11
Triple Crown Low Starch 13 6 18 15
Nutrena Safe Choice 14 7 15 22
Purina Ultium 11.7 12.4 18.5 16
Pennfield EnduroEvent Ener-G 10 10 15 26
Buckeye Unbeetable 12.5 8 12 34
SS Legends 12 Equitech 10 10 10 34.5
What is cut-off level???
How much is “low”???
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Common Horse Feed IngredientsFeedstuff Sugar (% DM) Starch(% DM) NSC (% DM)Alfalfa Pellets 7.20 2.30 9.30
Alfalfa Cubes 8.30 2.00 10.20
Rice Bran 6.20 17.70 21.20
Oats 4.80 44.40 54.10
Corn 3.70 70.30 73.30
Barley 6.00 53.70 61.70
Beet Pulp 10.70 1.40 12.30
Wheat Bran 8.30 22.80 31.10
Soybean Hulls 4.30 1.90 6.30
Wheat Middlings 10.10 26.20 32.00
Soybean Meal 14.30 2.10 16.20
www.equianalytical.com
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Feeds & Molasses• Pure cane molasses 25% water, 50% sugar• Commercial horse feeds
– filtered and processed, – inhibit mold growth, change color, improve flow rate and
prevent freezing– app. 40% sugar
• Example: Feed that is 10% molasses, 1 lb feed = 4% sugar.– Feeds vary in molasses content from 0 to 20%– Molasses in “molassed beet pulp” is negligible (less than 2%)
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Countermeasures• Grazing Management
– Restricted grazing regimes• Avoid cold nights followed by
sunny days• Early AM vs. afternoon• Overcast days best• Shaded pasture• Avoid stressed forages• Consider dry-lot when risks
– Feed low NSC hay and feed to meet nutrient requirements
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• Grazing Muzzles– Restricts grazing to
small amounts– Restricts grazing to tops
of leaves• concentrations of NSC
tend to be lowest
– Exercise not restricted
Countermeasures
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Countermeasures• Hay Selection
– Determine NSC content and select hay less than 10% NSC, mature hay usually best
• Feed Selection– Select nutrient dense low NSC feeds
• Weight management– Short term high doses of Levothyroxine have been shown to
reduce weight and increase insulin sensitivity (Frank et al., 2006)• Exercise
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Misperceptions• No data for association of equine IR, Laminitis
and EMS with iron, magnesium, chromium or other minerals
• Avoid “metabolic” supplements• “NSC is bad for all horses”
– Some classes of horses (ie. racehorses) require high amounts of NSC for readily available energy
– Low NSC feeds are for a small population of horses
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Take Home Message• Determine if your horse is at risk before implementing
countermeasures• Most horses are not considered “at risk”• Only a few individuals within a herd may be susceptible
to dietary laminitis…most often those that are thrifty• If your horse is truly at risk, dietary and weight
management are the keys to laminitis avoidance
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AcknowledgmentsDr. Tania Cubitt
Virginia Tech MARE CenterMichigan State University
eXtension
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