The objective of this experiment was to determine the respective effects of level of intake and of the amount of volatile fatty acids (VFAs) present in the rumen on VFA ruminal absorption. In a factorial design, six ewes received a hay diet either at 126 or at 73% of energy maintenance requirements. Their capacity of absorption of VFAs was evaluated by the method of temporarily isolated rumens, in which the rumen was filled with solutions containing high or low amounts of VFAs. Rate of absorption (amount of VFAs absorbed per hour) was significantly higher, by 32% on average, in sheep fed the high intake than in sheep fed at low intake. The proportion of initial VFAs absorbed did not depend on the concentration of VFAs introduced in the rumen, so that the amount of VFAs absorbed varied as the concentration of VFAs introduced in the rumen. The decrease in intake resulted in a decrease by 32% in the rate of absorption of total VFAs. No interaction between concentration of VFAs and previous intake was observed. This suggests that the capacity of the rumen to absorb VFAs is reduced at low intake even if low amounts of VFAs are available.

Summary ― The ability of the rumen to absorb the same quantity of VFA with 4 animals previously fed with 2 levels of intake was tested. Animals received maintenance (Pi) exprimées en mmoilh ou en % de la quantité initiaielh pour la comparaison des 3 AGV L'ordre des vitesses d'absorption (%lh) était C4 > C3 > C2. L'absorption d'eau n' a pas varié significativement entre les périodes mais la vitesse d'absorption des AGV (mmollh) a été significativement réduite après la période de sous-nutrition. La composition de la solution n'a pas eu d'effet sur la vitesse d'absorption des AGV (% l h). ). AGV l absorption l sous-nutrition

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