Influence of herbage species, cultivar and cutting date on fatty acid composition of herbage and lipid metabolism during ensiling

The fatty acid (FA) concentration of herbage and lipid metabolism in silage, mainly oxidation and lipolysis, of different species (perennial ryegrass, red clover and white clover) and three cultivars of white and red clover at three cutting dates in the growing season (April, July and October) were studied. FA concentration and composition was strongly affected by species and cutting date. Perennial ryegrass had lower concentrations of C16:1, C18:0, C18:1 and C18:2 than red and white clover. Within red and white clover, the effect of cultivar was small. Oxidation of C18:3 during wilting was different between species and cutting date despite similar wilting conditions. Lipolysis in silage was also influenced by cutting date, species and to some extent by cultivar. Furthermore, in some cuts silages of red and white clover displayed a lower lipolysis than silage of perennial ryegrass. On average, over the three cutting dates proportionately 0.903, 0.864 and 0.857 of the membrane lipids in perennial ryegrass, red clover and white clover were hydrolysed during ensiling. In red clover this could be due to the lipid-protecting properties of polyphenol oxidase (PPO) activity. This was not observed in perennial ryegrass or white clover. Nevertheless, differences in lipolysis in silage between cultivars of red clover were not correlated with PPO activity