Ruminal degradation of mountain pastures infested by Euphorbia polygalifolia in cattle and sheep: effect of previous grazing in invaded areas

Six cows and eight ewes were distributed in four paddocks according to a factorial design, 2 species (cattle vs sheep) × 2 grazing managements (grazing in pastures invaded vs non‐invaded by Euphorbia polygalifolia), to study the ability of sheep and cattle to ruminally degrade mountain pastures containing E. polygalifolia, as well as the influence of previous grazing in invaded areas. After a period of 17 days, rumen fluids were collected and used as microbial inoculum to examine in vitro fermentation rates and ruminal parameters of infested and non‐infested pastures. Results on parameters of gas production, extent of degradation, ammonia concentration and volatile fatty acid production of infested pastures indicate a better fermentation of this substrate in sheep than in cattle. The absence of noticeable differences when the pasture without this species of spurge was incubated suggests that most variation between ruminant species can be attributed to the presence of E. polygalifolia. The positive effect of previous grazing in invaded areas on rates of gas production, extent of degradation and ammonia concentration supports the hypothesis that the ability to degrade infested pastures may be enhanced by previous consumption, probably through an adaptation of the rumen microbiota. Copyright © 2006 Society of Chemical Industry