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

Abstract

Grasses are a source of nutrients for grazing horses. However, water-soluble carbohydrates (WSCs) 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 selected cultivars of cool-season grasses and profile the phenolic compounds. Total phenolics and WSC were quantified in “Linn” and “Calibra” perennial ryegrass (PRG), “Cajun II” tall fescue (Cajun TF), “Persist” orchardgrass (OG), and “Ginger” Kentucky bluegrass (BG), collected in the morning and afternoon of late April, early May, and late May. WSCs were higher in the afternoon (P < .0001), and afternoon concentrations differed among cultivars (P = .011) and decreased by late May (P < .0001). Total phenolics, initially highest in Calibra PRG and Persist OG, decreased or remained constant from late April to late May, except in Persist OG (P < .0001). Total phenolics decreased in the afternoon in Persist OG and Calibra PRG (P = .015). High-performance liquid chromatography revealed similar phenolic profiles in Calibra PRG, Linn PRG, and Cajun TF. These differed from the profiles of Ginger BG and Persist OG. Major peaks were characterized by liquid chromatography coupled to mass spectrometry. The cultivars had a diversity of phenolic compounds possibly worth exploring for properties that may interact with those of WSC to impact equine health.