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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1419v1 87/4/1366    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Malecky, M. Articles by Broudiscou, L. P. Search for Related Content PubMed PubMed Citation Articles by Malecky, M. Articles by Broudiscou, L. P.

Disappearance of nine monoterpenes exposed in vitro to the rumen microflora of dairy goats: Effects of inoculum source, redox potential, and vancomycin

Institut National de la Recherche Agronomique–AgroParisTech, F75005 Paris, France

¹ Corresponding author: laurent.broudiscou{at}agroparistech.fr

This in vitro study evaluated the roles of diet type and redox potential in the degradation of linalool, (E)- and (Z)-β-ocimene, -phellandrene, (–)-β-pinene, (–)--pinene, (+)--pinene, sabinene, and -terpinene when incubated with rumen microflora, and it provided information on the time course of their disappearance. The 9 monoterpenes are found in the winter and spring diets of dairy goats in northwestern Mediterranean grazing systems. The diets were individually exposed to rumen microflora for 3 h in 17-mL culture tubes at a concentration of 4 µL/L. The mixed flora of the inoculum was controlled by the use of vancomycin (eliminating gram-positive bacteria) and by the energy source (starch vs. structural polysaccharides) on which rumen microflora had been grown. Redox potential was controlled by addition of L-cysteine-hydrochloride. The preliminary adaptation of microbial inoculum to a diet rich in structural carbohydrates reduced the recovery yields of (E)- and (Z)-β-ocimene, (–)-β-pinene, (–)--pinene, (+)--pinene, and sabinene (P < 0.01), whereas vancomycin was without effect. The effect of carbohydrate source likely stems from the specific composition of the microbial community rather than from its acidogenic capacity. Reducing the culture redox potential by 50 mV reduced the recovery yields of linear and monocyclic terpenes (P < 0.02), and the culture redox potential interacted with the inoculum source for (E)- and (Z)-β-ocimene and for -phellandrene. The time course of terpene disappearance was studied by exposing terpenes to a rumen microflora adapted either to starch or to fiber for 3, 6, or 24 h. The degraded fraction reached a plateau within 3 h for -phellandrene and for all the isomers of β-ocimene and pinene with the fiber-adapted microflora as well as with both inocula for -terpinene. With the starch-adapted microflora, this steady state was reached for most other terpenes within 6 h of incubation. Sabinene was the only compound still disappearing after an incubation period of 6 h. Biotic and environmental variables in the rumen affected terpene degradation in a way that can alter the dietary terpene profile and possibly its influence on animal product characteristics.

Key Words: goat • monoterpene • redox potential • rumen microflora • vancomycin