Utilization of tanniniferous feeds.2. Effect of tanniniferous feed on nutrient digestibility, gas production and tannin degradation products in cattle in vitro

Abstract

Six total mixed rations (TMR) containing 0, 40,60,80, 100, 120 g tanninlkg dry matter, using Acacia nilotica pods as a sources oftannin, were assessed in vitro for nutrient digestibility and gas production with rumen fluid ofcrossbred cattle. Degraded products oftannins have been identified using TLC and HPLC at different hours ofincubation. In vitro digestibility of dry matter (IVDMD), organic matter (IVOMD) and crude protein (IVCPD) decreased with increased levels of tannins in the total mixed rations. Decline in crude protein digestibility was much more prominent than dry matter and organic matter digestibility. In vitro gas production was also reduced with increased levels of tannins in the TMR during first stage kinetic (0-24 h incubation) and tended to increase during the second stage kinetic (24-48 h incubation). Gallic acid, phloroglucinol, resorcinol and catechin were identified at different hours ofincubation. Tannin metabolites were noticeable on TLC after 18 h incubation and persisted till 48 h of incubation. Phloroglucinol and resorcinol were the major end products of tannin degradation while catechin and gallate were produced in traces. It is inferred that tannins of Acacia nilotica pods reduced the in vitro nutrient digestibility, however, ruminal microbes of cattle were capable to degrade the tannin ofAcacia nilotica pods without pre-exposure to this diet.