Countermeasures For Equine Laminitis (Mc Intosh)

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COUNTERMEASURES FOR EQUINE LAMINITIS

Dr. Bridgett McIntoshUniversity of Tennessee


Meet our presenter:

Dr. Bridgett McIntoshUniversity of Tennessee

Dr. Tania CubittPerformance Horse NutritionQuestion facilitator:


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


• 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?


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.


Hoof Anatomy

http://www.uoguelph.ca (Gunn, 2009)

Coffin bone also called “Pedal Bone” or “P3”


Cross section of the equine hoof

•Lamina (L)

•Coronary Band (C)


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


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

Thanks to our sponsor:Thanks to our sponsor:

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


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


• 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


Glucose

Insulin

(Rodiek et al., 1991)Slide modified from Kibby Treiber


Glucose

Insulin

(Clarke et al., 1990; Valentine et al., 2001)Slide modified from Kibby Treiber


Hindgut pH

Gram negative bacteria killed off

Gram positive lactate producing bacteria


Damage to cecum from high doses of starch

Kreuger et al., 1986

LAMINITIS!NORMAL


ANIMAL FACTORSObesityInsulin resistanceMetabolic syndrome”

DIETARY FACTORSNonstructural Carbs

- Pasture Conditions- Harvest Conditions

- Feed Ingredients

RISK FACTORS FOR RISK FACTORS FOR LAMINITISLAMINITIS


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


Obesity/Regional Adiposity



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)



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



Equine Metabolic Syndrome• Characterized by:

– Obesity/Regional Adiposity

– Insulin Resistance– Laminitis



Pasture, Hay, Feed Ingredients• Nonstructural carbohydrates (NSC)

–Starch–Sugar–Fructan

Dietary Risk Factors


Plant Carbohydrates

Cell contents Cell wall

FructanFructose StarchSucrose Hemicellulose Cellulose

Rapidly Fermented (Hindgut)

Glucose

Hydrolyzed (small Intestine)

Slowly Fermentable (Hindgut)


• Starches– Cereal Grains– Legumes

• Sugars and Fructan– Cool Season Grasses

Dietary Risk Factors


• 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


• 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


Five 42 hour trials


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)


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, %


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

Thanks to our sponsor:LAB 2 PROCEDURE

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


AUGUST

LAB 2 PROCEDURE

0600 1800 0600 180002468

10121416182022242628

SugarFructanStarch

NSC

Sample h

% D

MNSC Pasture Profiles


JANUARY

LAB 2 PROCEDURE

0600 1800 0600 180002468

10121416182022242628

Sugar

FructanStarch

NSC

Sample h

% D

MNSC Pasture Profiles


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


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


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


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 …



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


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


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.


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


• 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


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


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…


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


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


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


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


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”???


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


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%)


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


• Grazing Muzzles– Restricts grazing to

small amounts– Restricts grazing to tops

of leaves• concentrations of NSC

tend to be lowest

– Exercise not restricted

Countermeasures


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


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


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


AcknowledgmentsDr. Tania Cubitt

Virginia Tech MARE CenterMichigan State University

eXtension


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Countermeasures For Equine Laminitis (Mc Intosh)