Long-chain alcohols did not improve predictions of the composition of tall fescue and red clover mixtures overn-alkanes alone

Abstract

Feed intake and diet choice affect production efficiency in livestock. Plant waxes, in particular n-alkanes, have been used as markers to predict intake and diet preferences. Still, when n-alkane profiles of plants within mixed swards are similar, they alone may not produce reliable predictions. Including long-chain alcohols (LCOHs) may help. In this study, the reliability of predicting forage mixtures was assessed using n-alkanes and LCOH separately and in combination. Reliability was characterized as the regression of observed on predicted fescue proportion in forage mixtures and the Kulczynski similarity index. Two technicians performed extractions of n-alkanes and LCOHs of pure red clover and ‘Fawn’ tall fescue, and nine mixtures of them. The concentrations of n-alkanes C27, C29, C31 and C33 and alcohols C26-OH, C28-OH and C30-OH were compared among forage mixtures and between technicians. Technicians were consistent in their measures of n-alkanes (P > 0·12), but differed in their measures of C26-OH and C28-OH (P < 0·002). Longer-chained compounds were more consistently quantified. Forage delineations were not improved by C26-OH. With n-alkanes alone, estimated and actual fescue proportions closely agreed. Including LCOH offered no improvement. Despite variation in measured concentrations between technicians, fescue and red clover mixtures were reliably predicted using n-alkanes alone.