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

Authors: Kagan, Isabelle; Davis, Brittany; SCHENDEL, RACHEL - University Of Kentucky

Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2023
Publication Date: 12/21/2023
Citation: Kagan, I., Davis, B.E., Schendel, R.R. 2023. 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. Grass and Forage Science. 78(4):536-546. https://doi.org/10.1111/gfs.12633.
DOI: https://doi.org/10.1111/gfs.12633

Interpretive Summary: Fructans are carbohydrates formed from chains of the sugar fructose. Often sucrose (table sugar) is a part of the chain. Fructans are found in cool-season grasses, and in other countries the amounts and lengths of fructans have been found to change at different times of year. Because fructans may have some positive effects on ruminant performance, understanding how fructans change during a grazing season may help to make grazing management decisions for ruminants. The purpose of this study was to examine changes in the amounts and types of fructans in timothy and tall fescue grown in central Kentucky. Amounts of long and short fructans, as well as a small sugar called raffinose, were measured in timothy and tall fescue harvested in April, June, August, and October for 2 consecutive years. Timothy had more raffinose than tall fescue in June. Most of the shortest fructans were more plentiful in tall fescue than in timothy in April. Tall fescue had more short fructan (4 to 8 sugar units long) than timothy in April, August, and October. Timothy had more long fructan (over 8 units long) than tall fescue in April, June, and October. In August, both grasses had very little long fructan, and little of most of the other sugars measured. Having a better understanding of seasonal changes in fructans may help in future studies of how grass fructans affect microbes in the rumen.

Technical Abstract: Fructans in cool-seaon grasses may have some positive effects on ruminant performance, and fructans of different lengths appear to be metabolized differently in the rumen. Hence, seasonal variation in grass fructan concentrations may impact ruminant performance. Long-chain fructan with degree of polymerization (DP) > 8, short-chain fructan (DP 4 to 8), raffinose, and several fructan trisaccharides were profiled and quantified in timothy (Phleum pratense L.) cultivar ‘Clair’ and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) 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 = 0.0017). Harvest date influenced species differences in raffinose (P = 0.0035), which was most abundant in timothy in June, and in 1-kestose and neokestose (P < 0.0001), which were most abundant in tall fescue in April. Harvest date influenced species differences in short- and long-chain fructan (P < 0.0001). Tall fescue had two- to threefold more short-chain fructan than timothy in April, August, and October. Timothy had two- to fivefold more long-chain fructan than tall fescue in April, June, and October. Understanding seasonal variation in fructan concentrations may inform future studies of effects of grass fructans on rumen microbiota.