Caracterização química e digestibilidade in vitro de leguminosas forrageiras tropicais com foco no efeito de compostos fenólicos e idade da planta

Abstract

It were evaluated the gas production from tropical legumes with forage potential, including sun hemp (Crotalaria juncea), indian rattlebox (Crotalaria spectabilis), pigeon pea (Cajanus cajan), perennial horse gram (Macrotyloma axillare), cowage (Mucuna aterrina) wild groundnut (Calopogonium mucunoides) stylosanthes Campo Grande (Stylosantis sp .) and jack-bean (Canavalia ensiformis),with different ages (47, 68, 89 and 110 days) and incubated in vitro (approximately 1 g dried matter sample / bottle) for up to 96 hours. The degree of bacterial adherence on these samples was measured by phosphorus content in the residue after 24 hours in vitro incubation. Assays were also conducted to evaluated the effect of adding polyethyleneglycol (PEG) and tanniferous extract of acacia on in vitro fermentation of legumes and pure substrates (starch, cellulose (Avicel) and calcium caseinate). The volume of gas (between 110ml and 89mL), the rate of fermentation (between 2,92% / h and 3,96% / h) and lag time (between 0.3 hours and 5.09 hours) as well as the degree of bacterial adherence (from 0,14 mg P / g residual DM and 1,07 mg P / g residual DM) varied between legumes and plant age. The degradation rate (R=-0.72, P <0.0001) and degree of bacterial adherence (R = -0,70 and P <0.0001) were negatively affected by the lignin content of tropical legumes. Moreover, the tannin content of legumes, or any tanniferous extract in samples of pure substrates showed no clear effect on in vitro fermentation. The addition of PEG, in turn, affected significantly all parameters of kinetics of gas production, which indicates that the use of this substance as a tannin inhibitor on in vitro assays need to be evaluated.