April 7, 2022
Emma Read, DVM, MVSc, DACVS, President
David L. Foley, CAE, Executive Director
Sally Baker, Director of Marketing & Public Relations
American Association of Equine Practitioners
4033 Iron Works Parkway
Lexington, KY 40511
Dear President Dr. Read, Mr. Foley, and Ms. Baker,
We are writing to you in reference to a post put up on the AAEP Facebook page April 5, 2022 regarding pasture-associated laminitis. The post was subsequently taken down, presumably due to the large volume of negative feedback on the content. We were disappointed in that action. It would have been more fruitful to have a dialog.
Please allow me to elaborate on why fructan is not the issue in pasture laminitis.
In 2006, van Eps and Pollitt reported the induction of laminitis by administering a bolus of pure chicory root oligofructose (a fructan) by stomach tube. The amount required was 7.5 g/kg to induce laminitis in one foot; 10 to 12.5 g/kg for systemic reaction and multifoot laminitis. For a horse to take in that much over a 24 hour period of grazing would require a pasture with 37.5% fructan on a dry matter basis. Perennial ryegrass
improved varieties growing under extreme conditions in areas of the world that are cool and rainy might have the potential to reach that level, at least transiently, but no grass in North America comes even close. The average difference between WSC (sugars + fructans) and ESC (sugars) is only 2% in the Dairy One database.
Crawford et al., 2007 fed 3 g/kg chickory fructan to ponies with and without a history of pasture laminitis. Despite a moderate drop in fecal pH from 6.89 to 6.18, there was no evidence of illness or laminitis, no increase in blood levels of fecal amines, or D-lactate (bacterial) which would indicate a compromised colonic barrier. They concluded there is a threshold for fructan to have negative effects.
In 2006, Trieber et al., reported following a herd of 160 ponies on pasture and found a prelaminitic metabolic profile was defined on the basis of body condition, plasma triglyceride concentration, RISQI, and MIRG. (RISQI and MIRG are proxies for insulin sensitivity.) Meeting > or = 3 of these criteria differentiated prelaminitic from never-laminitic group ponies with a total predictive power of 78%. Onset of spring laminitis
in the ponies at risk coincided with a flush of clover and increased pasture starch, not fructan.
Coleman et al., 2018 did a large epidemiological study of horses in North America and identified obesity and regional adiposity, and pre-existing endocrinopathy as risk factors.
Menzies-Gow et al., 2017 followed 446 animals for a period of 3 years and monitored multiple factors to identify those which would be predictive of laminitis developing at pasture. They concluded: “Risk factors for future laminitis prior to disease occurrence include low plasma adiponectin and high serum basal insulin or insulin post-dexamethasone concentrations. “
Fructan-induced laminitis is a carbohydrate overload model with SIRS, endotoxemia, fever and diarrhea – none of which are seen with pasture laminitis. There is no question endocrinopathic laminitis is behind spring
pasture laminitis. Borer et al., 2016 demonstrated chicory fructan produces minimal changes in glucose or insulin which is not surprising considering fructan is not a sugar, and not absorbed. It is a storage form of carbohydrate composed of fructose chains but is no more a sugar than cellulose, which is a chain of glucose
The AAEP post further went on to suggest legumes would be safe. This is not correct. In addition to Trieber’s 2006 study documenting the starch in clover pasture as a trigger, Kagan et al., 2020 compared red and white clover samples collected in the morning and afternoon and found significant diurnal variation in starch content
from morning to afternoon; red clover 13-51 g/kg; white clover 24-52 g/kg freeze-dried weight. At 10 kg/day dry matter intake, this represents a range of 130 to 520 grams of starch intake alone. This, combined with the WSC fraction which, given the lack of fructan, would be comprised of simple sugars, led the authors to conclude that grazing clover is not recommended for horses at risk of endocrinopathic (insulin-induced)
In addition to the post on the AAEP Facebook page, multiple materials on the AAEP.org site have similar inaccurate information, e.g.,
Geor 2013 https://aaep.org/sites/default/files/issues/GeriatricGeor2.pdf refers to restricting pasture access because of fructan. Parks 2016 https://aaep.org/issue/laminitis-0 No mention of testing and treatment for endocrinopathic
laminitis despite the fact this explains the vast majority of cases. Frank 2018 https://aaep.org/sites/default/files/issues/proceedings-08proceedings-z9100108000341.PDF
does discuss endocrinopathic issues, but also alludes to gastrointestinal overload as a cause of pasture laminitis.
We urge you to take the above into consideration and update your information on pasture laminitis. Correct treatment and future management of these animals depends on it.
Eleanor M. Kellon, VMD
Owner, Equine Cushing’s and Insulin Resistance on groups.io
Veterinary Consultant, Equine Cushing’s and Insulin Resistance Group Inc.
Kathleen M. Gustafson, PhD
Research Director, Equine Cushing’s and Insulin Resistance Group Inc.
Nancy C. Collins
President, ECIR Group Inc.
The ECIR Group Inc., 2307 S. Rural Road, Tempe, AZ 85282 ! of !2 3