In vitro effects of and interactions between tannins and saponins and fate of tannins in the rumen

Abstract

The rate of fermentation of hay was not affected by purified tannins from Quercus incana and Dichostachys cinerea at 0.13 mg ml-' of the in uitro medium whereas a decrease of 4% in the rate was observed for Acioa barmi tannins at this level. At 0.23 mg and 0.47 mg of tannins per ml, the decrease in rate varied from 4 to 13% and 13 to 20%, respectively. The decrease in in uitro true digestibility of dry matter was 3, 6 and 7% for Q incana, D cinerea and A barteri, respectively, at a tannin concentration of 0.47 mg ml-', and 17, 21 and 27%, respectively, at 0.93 mg ml-'. There was no change in the potential extent of digestion up to 0.47 mg ml-' for any of the tannins studied. These results suggested that the rate of digestion is affected to a greater extent than the potential extent of digestion or the in oitro true digestibility and that different tannins even at the same level have different degrees of effect. Tannin-saponin interactions were studied using tannic acid (TA), quebracho tannin (QT) and quillaja saponin (S) at different concentrations (0.2, 0.4 and 0.6 mg ml-') alone and in combination with each other. The decrease in the rate of digestion and true digestibility was additive when both the TA and the S were present. Similar results were obtained when TA was replaced by QT except that the effects with QT were more marked as compared to TA at the same concentration. Saponins had little effect on the potential extent of digestion and true digestibility. These tannins also decreased the production of short-chain fatty acid (SCFA) and their molar proportions (acetate decreased whereas propionate increased). Efficiency of microbial protein synthesis, expressed as the ratio of ' ' N incorporation per unit of SCFA production, was higher with both S and the tannins studied. A substantial amount (71-93%) of tannins soluble in aqueous acetone was released from leaves of some trees and shrubs on incubation in the in oitro medium for 48 h. The rumen liquor was not capable of degrading oligomeric condensed tannins.

Effects of long-term supplementation of chestnut and valonea extracts on methane release, digestibility and nitrogen excretion in sheep

“…A number of in vitro studies have indicated that tannin supplementation may improve the efficiency of microbial protein synthesis (Makkar et al, 1995;Bhatta et al, 2001). Makkar (2003) suggested that low levels of tannins have the potential to modulate rumen fermentation towards increased microbial protein synthesis.…”

Bioactivity of phytochemicals in some lesser-known plants and their effects and potential applications in livestock and aquaculture production systems

“…The higher efficiency of digestion observed in systems containing low levels of tannins could be due to specific inhibition or enhancement of a group(s) of micro-organisms. The decrease in the rate of digestion of feeds by low levels of tannins (Makkar et al, 1995a) could also help synchronise the release of various nutrients, which in turn might be responsible for increased microbial efficiency.…”

Estimativa da degradabilidade ruminal de alimentos utilizando a técnica de produção de gás em bovinos, ovinos e caprinos

“…Outra notável diferença entre esses alimentos deve-se ao menor teor de FDN (Tabela 1) no feno de alfafa e, por conseguinte, maior teor de carboidratos não estruturais (SDN), o que permite à alfafa ser classificada como um volumoso de alta qualidade. Esse fato já havia sido preconizado por Schofiled & Pell (1995), segundo os quais a contribuição de gás a partir da fração SDN é maior para as leguminosas do que para as gramíneas.…”

“…As vantagens dessa técnica sobre as outras técnicas in vitro, como a de Tilley & Terry (1963), para a avaliação de alimentos, foram destacadas por Blümmel & Ørskov (1993) e Makkar et al (1995). Outros métodos in vitro são baseados em mensurações gravimétricas que seguem o desaparecimento do substrato (componentes que podem ou não contribuir para a fermentação), enquanto a mensuração de gás concentra-se no surgimento de produtos de fermentação (substâncias solúveis, mas não fermentáveis, não contribuem para a produção de gás).…”