Stability of fatty acids during wilting of perennial ryegrass (Lolium perenne L.): effect of bruising and environmental conditions

Abstract

Oxidation of fatty acids (FA) during field wilting of herbage could cause extensive losses of polyunsaturated FA. Recent studies showed a variable effect of wilting on the losses of FA. This suggests that environment and management conditions influence the loss of FA during wilting. The present study investigated the stability of FA in untreated and mechanically bruised perennial ryegrass, wilted under field conditions for 0, 12, 24, 36 and 48 h, or wilted under controlled climate conditions at three temperatures (15, 25 or 35 °C) and two light (dark or light) regimes to dry matter (DM) contents of 425, 525 or 625 g kg(-1). During 48 h of field wilting, the total FA content declined (15.2 to 11.9 g kg(-1) DM) consistently, despite an increase in herbage DM content (197 to 676 g kg(-1)). Under controlled climate conditions, the herbage total FA content declined (15.1 to 11.7 g kg(-1) DM) mainly during the prolonged (56 to 62 h) initial drying to a DM content of 425 g kg(-1) and did not decline with further drying to DM contents of 525 and 625 g kg(-1). The decline in total FA was associated with a parallel decline in C18:3 content under field (9.15 to 6.36 g kg(-1) DM) and controlled (9.12 to 6.15 g kg(-1) DM) conditions. Concomitantly, the proportion of C18:3 in total FA decreased, whilst the proportion of C16:0 and C18:0 increased. Lower losses of FA (P<0.05) were observed at 15 °C compared to 25 and 35 °C. Light did not affect the losses of FA during wilting. The duration of the wilting period mainly affected the changes in FA content and composition. Stability of FA in herbage could be increased by minimising the duration of wilting.