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Evaluating digestibility and toxicity of native warm-season grasses for equines

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dc.contributor.authorGhajar, Shayanen
dc.contributor.authorMcKenzie, H. C.en
dc.contributor.authorFike, John H.en
dc.contributor.authorMcIntosh, B.en
dc.contributor.authorTracy, B. F.en
dc.contributor.departmentSchool of Plant and Environmental Sciencesen
dc.contributor.departmentLarge Animal Clinical Sciencesen
dc.date.accessioned2021-06-11T15:14:53Zen
dc.date.available2021-06-11T15:14:53Zen
dc.date.issued2021-01en
dc.description.abstractIntroduced cool-season grasses are dominant in Virginia's grasslands, but their high digestible energy and nonstructural carbohydrate (NSC) levels pose a risk for horses prone to obesity and laminitis. Native warm-season grasses (NWSGs) have lower digestible energy and NSC levels that may be more suitable for horses susceptible to laminitis. Although NWSGs have desirable characteristics, they are novel forages for horses. Little is known about NWSG intake or potential toxicity to horses or how grazing by horses may affect NWSG swards. The overall objectives of this research were to 1) assess voluntary intake, toxicological response, and apparent digestibility of NWSG hays fed to horses; and 2) evaluate the characteristics of three NWSG species under equine grazing. For the first objective, a hay feeding trial using indiangrass (IG) (Sorghastrum nutans) and big bluestem (BB) (Andropogon gerardii) was conducted with nine Thoroughbred geldings in a replicated 3 x 3 Latin square design. Voluntary dry matter intake of IG and BB hays by horses were 1.3% and 1.1% of BW/d, lower than orchardgrass (Dactylis glomerata), an introduced cool-season grass, at 1.7% of BW/d (P = 0.0020). Biomarkers for hepatotoxicity remained within acceptable ranges for all treatments. Apparent dry matter digestibility (DMD) did not differ among hays, ranging from 39% to 43%. NSC levels ranged from 4.4% to 5.4%, below maximum recommended concentrations for horses susceptible to laminitis. For the second objective, a grazing trial was conducted comparing IG, BB, and eastern gamagrass (EG) (Tripsacum dactyloides) yields, forage losses, changes in vegetative composition, and effects on equine bodyweight. Nine, 0.1-ha plots were seeded with one of the three native grass treatments, and each plot was grazed by one Thoroughbred gelding in two grazing bouts, one in July and another in September 2019. IG had the greatest available forage, at 4,340 kg/ha, compared with 3,590 kg/ha from BB (P < 0.0001). EG plots established poorly, and had only 650 kg/ha available forage during the experiment. Grazing reduced standing cover of native grasses in IG and BB treatments by about 30%. Horses lost 0.5-1.5 kg BW/d on all treatments. Findings suggest IG and BB merit further consideration as forages for horses susceptible to obesity and pasture-associated laminitis.en
dc.description.notesThis activity was funded, in part, by the College of Agriculture and Life Sciences Pratt Endowment at Virginia Tech.en
dc.description.sponsorshipCollege of Agriculture and Life Sciences Pratt Endowment at Virginia Techen
dc.description.versionPublished versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1093/tas/txaa224en
dc.identifier.eissn2573-2102en
dc.identifier.issue1en
dc.identifier.othertxaa224en
dc.identifier.pmid33501415en
dc.identifier.urihttp://hdl.handle.net/10919/103784en
dc.identifier.volume5en
dc.language.isoenen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.subjectequineen
dc.subjectforageen
dc.subjectnative grassesen
dc.subjectpastureen
dc.titleEvaluating digestibility and toxicity of native warm-season grasses for equinesen
dc.title.serialTranslational Animal Scienceen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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