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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #361230
Title: Effects of harvest date, sampling time, and cultivar on total phenolic concentrations, water-soluble carbohydrate concentrations, and phenolic profiles of selected cool-season grasses in central Kentucky

Author
item Kagan, Isabelle
item GOODMAN, JACE - University Of Kentucky
item Seman, Dwight
item LAWRENCE, LAURIE - University Of Kentucky
item SMITH, S. RAY - University Of Kentucky

Submitted to: Journal of Equine Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2019
Publication Date: 6/18/2019
Citation: Kagan, I., Goodman, J.P., Seman, D.H., Lawrence, L.M., Smith, S. 2019. Effects of harvest date, sampling time, and cultivar on total phenolic concentrations, water-soluble carbohydrate concentrations, and phenolic profiles of selected cool-season grasses in central Kentucky. Journal of Equine Veterinary Science. 76:86-93. https://doi.org/10.1016/j.jevs.2019.05.005.
DOI: https://doi.org/10.1016/j.jevs.2019.05.005

Interpretive Summary: Cool-season grasses produce water-soluble carbohydrates, which may have a role in pasture-associated laminitis, a disease that affects about 90,000 horses annually in the U.S. alone. Cool-season grasses also produce phenolic compounds, small organic molecules which often protect against ultraviolet light, microbes, or herbivores in various plants. Water-soluble carbohydrates and phenolic compounds were quantified in five different cool-season grasses collected in the morning and afternoon of three springtime harvest dates. Several phenolic compounds were identified. Water-soluble carbohydrates were more abundant in the afternoon, while total phenolic compounds were either more abundant in the morning or not different between morning and afternoon. Both types of molecules were more abundant in the first growth of grass than in the regrowth (3 weeks after cutting). A cultivar of orchardgrass (Dactylis glomerata, cultivar Persist) had the most phenolic compounds, and a cultivar of Kentucky bluegrass (Poa pratensis, cultivar Ginger) had the least. The types and amounts of individual phenolic compounds varied among the grasses. Some of these phenolic compounds, because they have known antimicrobial properties, may be worth exploring for potential benefits to equine health.

Technical Abstract: Grasses are a source of nutrients for grazing horses. However, water-soluble carbohydrates (WSC) of grasses have been implicated in some equine health issues. Grasses also contain phenolic compounds, whose sensory and antimicrobial properties may affect forage intake by horses and horse health. The goals of this study were to assess factors affecting phenolic and WSC concentrations in five cultivars of cool-season grasses, and to profile the phenolic compounds. Total phenolics and WSC were quantified in perennial ryegrass “Linn” and “Calibra”, Kentucky bluegrass “Ginger”, tall fescue “Cajun”, and orchardgrass “Persist”, collected in the morning and afternoon of late April, early May, and late May. WSC was highest in the afternoon (P = 0.006) and decreased by late May in all cultivars except Ginger (P < 0.0001). Total phenolics decreased between late April and late May in all cultivars except Ginger and Persist (P <0.0001), and decreased in the afternoon in Persist and Calibra (P = 0.015). Persist had the most total phenolics, followed by Calibra, then Linn and Cajun, with Ginger having the least (P < 0.0001). High-performance liquid chromatography (HPLC) revealed similar phenolic profiles in Calibra, Linn, and Cajun. These differed from the profiles of Ginger and Persist. Major peaks were characterized by liquid chromatography coupled to mass spectrometry (LC-MS). The cultivars had a diversity of phenolic compounds possibly worth exploring for properties that may interact with those of WSC to impact equine health.