Seasonal and species variation in raffinose, short-chain fructan, and long-chain fructan accumulation in tall fescue (Festuca arundinacea Schreb.) and timothy (Phleum pratense L.) grown in Central Kentucky

Fructans in cool-season grasses may have some negative effects on equine health. However, they may have positive effects on ruminant performance, and fructans of different lengths appear to be metabolized differently in the rumen. Hence, seasonal variation in fructan concentrations may impact equine and ruminant performance. Long-chain fructan with degree of polymerization (DP) > 8, short-chain fructan (DP 4 to 8), raffinose, and three fructan trisaccharides were profiled and quantified in timothy (Phleum pratense L.) cultivar ‘Clair’ and tall fescue (Festuca arundinacea Schreb.) cultivar ‘Cajun II’ harvested in April, June, August, and October of two consecutive years in central Kentucky. Harvest year influenced concentrations of long-chain fructan (p = .0017). Harvest date influenced species differences in raffinose (p = .0035), which was most abundant in timothy in June, and in 1-kestose and neokestose (p < .0001), which were most abundant in tall fescue in April. Harvest date influenced species differences in short- and long-chain fructan (p < .0001). Tall fescue had two- to three-fold more short-chain fructan than timothy in April, August, and October. Timothy had two- to five-fold more long-chain fructan than tall fescue in April, June, and October. Species choice and weather patterns may have contributed to relatively low concentrations of all the carbohydrates measured in this study. Fermentation or feeding studies could help to determine if the concentrations present could affect equine health or ruminant performance.