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Nonstructural Carbohydrate Content of Weeds Commonly Found in Drylots
Diets high in carbohydrates are a known trigger for laminitis. One of the most effective management tools for limiting carbohydrate intake is confining a horse to a drylot and feeding a diet low in non-structural carbohydrates (NSC). A diet ≤ 12% NSC is recommended for horses diagnosed with laminitis, obesity, or equine metabolic syndrome. Recent reports from horse owners indicated laminitic horses housed in weedy drylots and fed low NSC diets were still experiencing recurring bouts of laminitis. The objective of this research was to determine NSC content of weeds commonly found in drylots housing laminitic horses. Ten horse farms in central Minnesota and western Wisconsin were enrolled in the study during spring and summer 2013. Study requirements included at least one horse with a history of laminitis housed in a weedy dry lot with restricted pasture access. Evidence of horse ingestion of the weeds was also required. Farm owners committed to providing access to the horse(s) and weedy drylot on three occasions during the 2013 grazing season. During each visit, weeds in the drylot were identified, and up to four of the most common weed species were harvested, frozen, and later sent to a commercial laboratory for nutrient analysis. Weed species harvested from the first farm visits were analyzed for forage nutritive values and results are presented on a dry matter basis. Weeds species collected during the second and third farm visits are currently being analyzed. Data were analyzed with the Proc Mixed procedure of SAS and reported as leas squares means. The four most common weeds collected during the first farm visits were prostrate knotweed (n=8), broadleaf plantain (n=4), purslane (n=3), and redroot pigweed (n=3). NSC content was different among the weeds (P<0.001). Mean NSC content was 10.7, 10.7, 8.5, and 5.7 for purslane, redroot pigweed, broadleaf plantain, and prostrate knotweed, respectively. NSC content of all weed species was below the recommended 12% threshold. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) content were not different among the weed species (P=0.09). ADF ranged from 22 to 33% and NDF ranged from 32 to 45%. The relatively low ADF and NDF levels may explain why the weed species were palatable to the horses. Although laminitic horses grazed weed species in a drylot, the low NSC content proves an unlikely connection between the weed species and the onset of laminitis.
Keywords: Weeds, Laminitis, Equine