The presentation discussed countermeasures for equine laminitis. Laminitis is a systemic inflammatory disease that manifests in the hoof and causes inflammation and degeneration of the lamina tissue connecting the hoof wall to the coffin bone. Dietary causes, such as nonstructural carbohydrates like starch and sugar in pasture, hay and grain, are a major risk factor for laminitis. The presentation reviewed research on the effects of pasture carbohydrate levels on insulin levels and digestion in grazing horses. Countermeasures discussed included grazing management, selecting low nonstructural carbohydrate hay and feed, weight management and exercise.

1. My Horse University and eXtension’s HorseQuest welcome you to this live Webcast. The presentation will begin promptly at 7:00 p.m. EST. COUNTERMEASURES FOR EQUINE LAMINITIS Dr. Bridgett McIntosh University of Tennessee

2. Meet our presenter: Dr. Bridgett McIntosh University of Tennessee Dr. Tania Cubitt Performance Horse Nutrition Question facilitator:

3. 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

4. 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?

5. 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.

6. Hoof Anatomy http://www.uoguelph.ca (Gunn, 2009) Coffin bone also called “Pedal Bone” or “P3”

7. Cross section of the equine hoof Lamina (L) Coronary Band (C)

8. 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

9. 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

10. Causes of Laminitis USDA- NAHMS, 2000 OVER 50% DIETARY CAUSES

11. 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

12. 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

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

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

15. Hindgut pH Gram negative bacteria killed off Gram positive lactate producing bacteria

16. Damage to cecum from high doses of starch Kreuger et al., 1986 LAMINITIS! NORMAL

17. ANIMAL FACTORS Obesity Insulin resistance Metabolic syndrome ” DIETARY FACTORS Nonstructural Carbs - Pasture Conditions Harvest Conditions Feed Ingredients RISK FACTORS FOR LAMINITIS

18. 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

19. Obesity/Regional Adiposity Risk Factors in Horses

20. 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

21. 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

22. Equine Metabolic Syndrome Characterized by: Obesity/Regional Adiposity Insulin Resistance Laminitis Risk Factors in Horses

23. Pasture, Hay, Feed Ingredients Nonstructural carbohydrates (NSC) Starch Sugar Fructan Dietary Risk Factors

24. Plant Carbohydrates Cell contents Cell wall Fructan Fructose Starch Sucrose Hemicellulose Cellulose Rapidly Fermented (Hindgut) Glucose Hydrolyzed (small Intestine) Slowly Fermentable (Hindgut)

25. Starches Cereal Grains Legumes Sugars and Fructan Cool Season Grasses Dietary Risk Factors

26. NSC Analysis 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) There are differences in nomenclature and techniques between laboratories

27. A Research Study on Equine Laminitis 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 Current Research

28. Five 42 hour trials

29. Nutrient content of forage a,b,c Feeds differ between months ( P < 0.05) Nutrient April May August October January Hay %CP 21.3 ± 1.4 a 14.0 ± 0.2 b 12.7 ± 0.2 c 12.9 ± 0.2 c 14.2 ± 0.3 b 11.3 ± 0.5 %ADF 25.4 ± 0.2 a 35.3 ± 0.2 b 36.9 ± 0.5 b 37.9 ± 0.2 b 39.1 ± 0.3 b 41.7 ± 0.4 %NDF 46.4 ± 0.3 a 64.2 ± 0.3 b 64.0 ± 0.7 b 66.2 ± 0.4 b 66.5 ± 0.5 b 62.1 ± 1.3 %NSC 20.3 ± 0.4 a 11.7 ± 0.4 b 9.2 ± 0.5 c 6.9 ± 0.2 c 7.1 ± 0.2 c 8.9 ± 0.1 % Sugar 18.9 ± 0.4 a 10.2 ± 0.4 b 7.6 ± 0.5 c 5.7 ± 0.2 c 6.1 ± 0.2 c 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 ± 0.4 a 2.8 ± 0.04 b 4.3 ± 0.1 a 3.8 ± 0.06 a 2.2 ± 0.09 b 1.6 ± 0.3 DE, Mcal/kg 2.8 ± 0.01 a 2.2 ± 0.01 b 2.1 ± 0.01 b 2.1 ± 0.01 b 2.1 ± 0.01 b 1.9 ± 0.02

30. Circadian variation: NSC April May

31. August October January October and January: Cloudy & Raining August: Hot & Humid LAB 1 PROCEDURE

32. LAB 2 PROCEDURE APRIL NSC Pasture Profiles

33. MAY LAB 2 PROCEDURE NSC Pasture Profiles

34. AUGUST LAB 2 PROCEDURE NSC Pasture Profiles

35. JANUARY LAB 2 PROCEDURE NSC Pasture Profiles

36. There was a relationship between temperature and pasture NSC

37. Solar Radiation (Sunlight) also affected NSC concentration in pasture

38. As humidity increased, NSC decreased in the pasture

39. 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 factors How does pasture NSC affect horses …

41. Insulin was higher in grazing horses in April In April, insulin was high in general APRIL MAY Insulin

42. August October January

43. Evident relationship in April NSC (r 2 = 0.507, P < 0.001) Insulin (r2 = 0.121, P < 0.001) Similar frequency ( P = 0.36) As pasture NSC fluctuated throughout the day, insulin followed the same pattern in grazing horses. When pasture NSC increased, insulin increased 15 minutes later.

44. Higher fecal lactate suggests rapid fermentation of sugars in grazing horses Lactate- April

45. Fecal pH was slightly lower in grazing horses Graze pH 6.9 (red) Control pH 7.4 (orange) Fecal pH- April

46. 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

47. 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…

48. 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

49. Hay & Pasture NSC www.equianalytical.com 2000-2006, 4,000+ samples Forage Type NSC (% DM) Low NCS (%DM) High NSC (%DM) Grass Hay 13.1 8.2 18.0 MMG Hay 12.5 8.4 16.7 Legume Hay 11.1 8.8 13.4 MML Hay 11.2 8.4 13.9 Grass Pasture 12.8 7.1 18.0 MMG Pasture 12.8 8.0 17.6

50. 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

51. 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

52. What are low NSC Feeds? What is cut-off level??? How much is “ low ”??? 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

53. Common Horse Feed Ingredients www.equianalytical.com Feedstuff 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

54. 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%)

55. 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

56. Grazing Muzzles Restricts grazing to small amounts Restricts grazing to tops of leaves concentrations of NSC tend to be lowest Exercise not restricted Countermeasures

57. 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

58. 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

59. 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

60. Acknowledgments Dr. Tania Cubitt Virginia Tech MARE Center Michigan State University eXtension

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