In vitro degradation by mixed rumen bacteria of 17 mono- and sesquiterpenes typical of winter and spring diets of goats on Basilitica rangelands (southern Italy)

BACKGROUND: Nine monoterpenes (delta-3-carene, p-cymene, limonene, beta-myrcene, (E)- and (Z)-beta-ocimene, alpha-phellandrene, alpha-terpinene, gamma-terpinene), seven oxygenated monoterpenes (1,8-cineole, linalool, (E)- and (Z)-linalool oxide, 4-terpinenol, alpha-terpineol, alpha-terpinolene) and one sesquiterpene (beta-cedrene) were investigated for their degradability in the rumen microbial ecosystem. These molecules were identified as dominant terpenes in the winter and spring diets of milking goats in Basilicata (southern Italy). RESULTS: All terpenes were tested at 3.33 mu L L-1 for 24 h using in vitro incubation with mixed rumen bacteria from dairy goats. Oxygen-containing compounds were those recovered at the highest levels (89% of (E)-linalool oxide, 93% of (Z)-linalool oxide, 91% of 1,8-cineole, 82% of terpineol and 72% of 4-terpinenol), except linalool. The linear alkenes beta-myrcene and beta-ocimene almost completely disappeared. Results were more variable among cyclic alkenes, with recovery rates ranging from 50% in the case of limonene to less than 1% for alpha-phellandrene. 17% of the only sesquiterpene of the group, beta-cedrene, was recovered. CONCLUSION: Recovery rates differed markedly among terpenes, partly in relation to the presence of oxygen and rings in the molecules. These observations should contribute to a better understanding of the changes in composition between the diet and milk terpenes. (C) 2008 Society of Chemical Industry