W 450 PASTURE-ASSOCIATED LAMINITIS Jennie L. Ivey, PhD, PAS, Assistant Professor Department of Animal Science

Good quality forage provides necessary Pasture-associated laminitis occurs when nutrients to grazing equids and should consume high levels of NSC. While NSC comprise the majority of a ’s diet. Most are present in all grasses during all growth horses can handle the transition from stages, concentrations are highest during rapid consuming preserved forages (primarily hay) growth, during times of direct sunlight, and to rapidly growing grasses easily, yet certain after times of stress (e.g., drought). When conditions can pose concern for individual horses consume high amounts of NSC, some horses. Unfortunately, some horses are more these pass through the small sensitive to the amount of starches, simple intestine and spill over into the hindgut where and fructans, also known as they are rapidly fermented. This rapid nonstructural carbohydrates (NSC), in lush fermentation causes the cecum to become green pastures and thus warrant specific more acidic and triggers multiple events, management attention. ultimately leading to laminitis. Additionally, horses that are obese or those suffering from Pasture-Associated Laminitis resistance may be more susceptible to pasture-associated laminitis. Equine laminitis is a painful, debilitating disease affecting the laminae within the . The laminae is a soft connective tissue Factors Affecting NSC Levels responsible for holding the coffin bone within in Grass the hoof capsule securely to the hoof wall Different grass species can result in varying (Image 1). In a horse suffering from laminitis, levels of NSC within pasture or hay. Cool- decreased blood flow to the laminae occurs season grass species tend to accumulate more resulting in inflammation, death of the laminae NSC as fructans, where warm-season grass tissue, and ultimately separation of the coffin species tend to accumulate more starches. As bone from the hoof wall in advanced cases. cool-season grasses grow most during the Lack of laminae integrity leads to downward cooler months, NSC concentrations of sugars, rotation of the coffin bone, and in severe starches and fructans tend to be higher in these laminitis cases, the coffin bone can rotate grasses during spring and fall months. through the sole of the horse’s hoof. This condition is also known as founder. While Numerous factors can cause NSC levels in laminitis can be caused by many different grasses to change from day to day. The time of scenarios — including repeated concussion on day can greatly impact NSC content in the hard ground (road founder), hormone grass, with the lowest concentrations from imbalance and grain overload — lush pasture approximately 2 a.m. to 9 a.m., and peak can cause pasture-associated laminitis or grass concentrations in the afternoon hours. Sunlight founder and can be further complicated by intensity will also cause an increase in NSC, as and . the sunnier the day, the more photosynthesis occurring in the plant, and thus higher amounts Aim to keep your horses at a moderate of NSC that are produced. Grasses in mostly body condition score (BCS, range from 4 to shady areas will tend to have lower NSC 6•, Image 2). Horses with an obese BCS content when compared to grasses in sunny ranging from 7 to 9 tend to display a locations. Cooler temperatures below 40 predisposition for laminitis bouts. degrees F overnight can also cause higher Reference UT Extension publication SP 782 concentrations of NSC. This is because the plant “Equine Welfare Series: The Body Condition will not utilize NSC stores overnight in lower Scoring System” and SP 795 “Equine temperatures, and the NSC will remain in the Welfare Series: Evaluating Your Horse’s leaves rather than being used for growth or for Weight and Condition” for how to assess energy storage in the root. Stress conditions your horse’s BCS and estimate body weight. that restrict plant growth, such as killing frosts, drought, non-lethal herbicide application and Current research shows NSC content is low soil fertility, can also increase NSC lowest in the overnight hours and peaks in concentration in the plant. the• late afternoon to early evening hours; therefore, it is best to allow horses to turn out at night and remove from pasture by Management Tips mid-morning. Keeping horses healthy and minimizing their risk of pasture-associated laminitis can be Use a grazing muzzle to limit your horse’s achieved though good management techniques. intake while out on pasture, especially Increasing awareness of the nutrients provided during• the spring and fall months, when by pastures, dried forages and other diet cool-season grasses are growing quickly. If components is essential in understanding how possible, limit grazing time or turnout in a to keep your horses healthy through the dry lot pasture, especially for horses with changing seasons. predispositions to laminitis or with a history of laminitic incidents.

Image 1: The laminae is a soft, connective tissue within the hoof, Image 2: Keeping horses at an ideal body condition responsible for holding the coffin bone to the hoof capsule. The score ranging from 4 to 6 can help prevent incidences laminae can be seen in this image as the dark red line, of pasture-associated laminitis due to insulin approximately 0.5 mm wide. (Image credit: Jennie Ivey, The resistance. (Image credit: Jennie Ivey, The University University of Tennessee) of Tennessee)

Equine Welfare Series: Shelter for Horses 2 Have your pasture, hay and other dietary occur anytime between mid-May through components tested to gain a general early June. •understanding of the NSC content in your horse’s diet. Horses that are insulin Use good pasture management including resistant or have had issues with laminitis regular mowing and pasture rotation. in the past should consume a diet that is 10 • percent or less in NSC when considering all For more information on nutritional sources of and fructan. management, forage testing, pasture-associated laminitis or pasture management, contact your Generally speaking, as plants mature from county Extension office. the leafy to pre-bud stage, NSC levels decrease• and fiber levels increase. The Resources exact nutrient content of forages is dependent on many factors including Spring pasture, fructans and founder. Larry pasture management, plant species, Lawrence, PhD and Stephanie Valberg, weather and geographic location. Remove DVM. University of Minnesota Extension. grazing muzzles and increase grazing time Pasture-Associated Laminitis. Raymond J. Geor, gradually to avoid any unintentional BVSc, MVSc, PhD. Veterinary Clinics of overgrazing during this transition period. North America; Equine Practice. 2005. Typically, in Tennessee this transition can Volume 25, pages 39-50.

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W 18-0121 11/17 Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development. University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and county governments 450 cooperating. UT Extension provides equal opportunities in programs and employment.