The effect of tannic acid on the degradation kinetics of protein and organic
matter (OM) of alfalfa hay was studied using four ruminally-cannulated sheep under
feeding oats hay as a sole diet. Alfalfa hay was treated with tannic acid (TA) at four
different levels, which were alfalfa hay +0% of TA (control; TO), alfalfa hay + TA at
1.5% of OM (T1.5), alfalfa hay + TA at 3.0 % of OM (T3.0) and alfalfa hay + TA at 4.5%
of OM (T4.5). Inhibition effect of TA on the disappearance of protein was significant
(P<O.05) up to 12 h of incubation for T4.5, however this effect was noticed up to 6 h
for T1.5 and T3. Tannic acid through the first 3h of incubation did not affect
disappearance of OM in alfalfa hay. The highest level of TA (T 4.5) had significantly reduced (P.05) OM
disappearances at incubation times of 6 and 12h. No significant effect was found for
TA on the disappearance of OM at the incubation times 24 and 48h. The amount of protein which was slowly degraded in the rumen was significantly
increased (P.05) in treated hay. The increasing of TA consistently decreased the
degradation rate (c) of protein. Tannic acid did not affect rapidly (a) and slowly (b) degraded fractions of
OM, however, the c of OM was significantly decreased (P.05) at T3.0 and T4.5.
These results suggested that lower level of TA (i.e. T1.5) appears to have a desirable
reduction effect on protein disappearance without shortening energy release from
OM.