The effect of drying temperature on in vitro dry‐matter digestibility and water‐soluble carbohydrate content of perennial ryegrass varieties

Abstract

In official forage grass variety trials in the UK, herbage samples are dried at 100°C or more to facilitate quick drying of the large numbers of samples that are currently needed. When assessing herbage quality, however, 80°C has been recommended as the highest temperature that can be used during drying without serious deterioration. Herbage from six perennial ryegrass varieties, which were known to show a range of variation in in vitro concentration of digestible dry matter (DMD) and water‐soluble carbohydrate concentration (WSC) during the vegetative phase of growth, was dried in an oven with forced ventilation at 100°C and at 80°C before analysis. Mean DMD over all varieties was slightly lower [6 g kg−1 dry matter (DM)] and mean WSC over all varieties was considerably lower (24 g kg−1 DM) at 100°C. Varieties differed in mean DMD over both drying temperatures by 37 g kg−1 DM and in mean WSC by 63 g kg−1 DM. There was, however, no significant interaction between variety and drying temperature for either DMD or WSC. Although drying at the higher temperature underestimated both DMD and WSC, it did not significantly alter the ranking of varieties or the range among them.

The Effect of Drying Methods on Water-Soluble Carbohydrates and Crude Protein Concentrations and Their Ratio in Two Perennial Ryegrass Cultivars

“…It is commonly accepted that the drying procedure may affect WSC concentration [39]; losses of 9 and 14% due to oven-drying versus freeze-drying of samples have been previously reported for grass-legume crops and perennial ryegrass, respectively [22,40]. Moreover, drying forage samples for 16 h at 100 • C has been shown to underestimate the WSC concentration compared to 80 • C, without altering the ranking between cultivars of perennial ryegrass [41]. Differences between the highest and lowest WSC concentration in the present study were not as large as those obtained in the spring growth of Timothy (Phleum pratense L.), where the WSC concentration in freeze-dried samples nearly doubled that of oven-dried samples (55 • C for 48 h) [42].…”

The effects of rate and timing of application of fertilizer nitrogen in late summer on herbage mass and chemical composition of perennial ryegrass swards over the winter period in Northern Ireland

“…A further sample was dried at 60°C for 48 h to determine the water‐soluble carbohydrate (WSC) concentration of the herbage by the method described by the Ministry of Agriculture, Fisheries and Food (1986). Although freeze drying gives results of non‐structural carbohydrate concentration closest to that of fresh herbage, oven drying is acceptable for most routine laboratory analyses (Jones and Moseley, 1993; Davies and Wilkins, 1998).…”