Lipid metabolism in mixtures of red clover (Trifolium repens) and perennial ryegrass (Lolium perenne) in lab scale silages and in vitro rumen incubations

Most often, farmers consider red clover an unattractive forage because of its low ensilability. Nevertheless, several in vivo and in vitro experiments also showed advantages of red clover silages such as decreased rumen biohydrogenation of polyunsaturated fatty acids. This has been attributed to a possible protective role of protein-bound phenols, with polyphenol oxidase playing a key role in their formation. This enzyme is active in red clover, but not in other green forages, such as, for example, perennial ryegrass. Therefore, the aim was to study the lipid metabolism within red clover/ryegrass mixtures in lab scale silages and during in vitro rumen batch incubations. Ensilability of red clover increased with higher proportions of ryegrass in the silage mixture. However, the lipid-protecting mechanism of red clover does not seem to occur in the co-ensiled ryegrass as lipolysis of polar lipids linearly increased with increasing proportions of ryegrass (86.0%, 91.6%, 89.9%, 93.1% and 95.6% in 60-day-old silages with 100/0, 75/25, 50/50, 25/75 and 0/100 red clover/ryegrass, respectively). Rumen lipolysis and biohydrogenation of C18:3n-3 and C18:2n-6 were negatively related to red clover proportions in the silage mixtures. The lipid-protective mechanism in red clover silages is confirmed, but it seems not to be transferred to lipids in co-ensiled forages.