Nutritive value for ruminants of winter oats-legume intercrops in organic cultivation

Winter oats were grown according to European organic farming regulations in monoculture (oats) and in intercropping with bard vetch (BAV), bitter vetch (BIV) or both legumes (MIX) to evaluate the effects of intercropping on forage yield and nutritive value for ruminants. The experiment was carried out as a randomised complete block design with four replications, and whole forage samples were obtained at two harvest dates (June and July). For both harvest times, all intercrops increased (P < 0.05) forage yield compared with oats, but forage crude protein content was only increased (P < 0.05) for BAV and MIX. Compared with oats, intercropping with BAV increased (P < 0.05) in vitro rate of gas production and total volatile fatty acid production, indicating a higher rate and extent of rumen degradation of BAV forage. In contrast, BIV forage harvested in June had lower (P < 0.05) rate of gas production and total volatile fatty acid production than June oats, but in general no differences in the in vitro rumen fermentation were detected between oats and BIV samples harvested in July. The results indicate that forage yield and quality can be enhanced by intercropping oats with BAV; however, intercropping with BIV increased yield but decreased nutritive value of the forage.