Effects of including bioactive legumes in grass silage on digestion parameters, nitrogen balance and methane emissions in sheep

The aim of this work was to investigate the effects of feeding sheep with silage mixtures containing bioactive legumes on intake and digestive parameters. The bioactive legumes used were sainfoin (SF, Onobrychis viciifolia) and red clover (RC, Trifolium pratense), which contain condensed tannins (CT) and polyphenol oxidase respectively. Five treatments were assigned to two groups of sheep according to a replicated 5 x 5 Latin square design. The five types of silages tested were, on a dry matter (DM) basis: pure timothy grass silage (Phleum pratense, control, T), three binary mixtures of T-SF, T-RC and RC-SF (500 g/kg each) and a ternary mixture of T-RC-SF (500, 250 and 250 g/kg respectively). The daily voluntary DM intake of silage mixtures containing both SF and RC was greater than for pure T silage, while the presence of SF resulted in lower organic matter digestibility compared to pure T. The rumen disappearance rate measured in situ increased linearly with the presence of SF and RC in silage. The nitrogen (N) digestibility was greater for pure T and T-RC than for T-SF, and the amount of N retained daily by the animals was greater for RC-containing silages than for T and T-SF. The methane (CH4) yield was greater for pure T than for the silage mixtures containing SF. We conclude that the presence of RC in silage could boost performances through intake and N retention, while SF-based mixtures appear to have reduced negative environmental impacts through the reduction of CH4 emissions.