10th International Scientific Conference on Agricultural Development and Sustainability

10th Symposium of Veterinary Medicine and Zootechnics

In vitro rumen degradability of tropical legumes and their secondary metabolites depends on inoculum source

Abstract

In this study, the in vitro apparent rumen degradability of organic matter (ARDOM) and plant secondary metabolites (ARDPSM) of three tropical legumes (Mucuna pruriens, Canavalia ensiformis, and Leucaena leucocephala) were assessed. For this, 3 experiments were set up, i.e., single end-point incubations (24 h) with ruminal inoculum from either Belgian or Cuban sheep as well as kinetic assessments inoculum from Belgian sheep. L-mimosine, L-canavanine, Concanavaline A (Con A), and trypsin inhibitor (TI) were the plant secondary metabolites (PSM) targeted in this study. In all three experiments, both bean as well as forage/bean meals of M. pruriens and C. ensiformis and their PSM were extensively degraded during 24 h incubation, irrespective of the inoculum source. Forage meal of L. leucocephala was considerably less degraded, with apparent ruminal degradabilities of 0.20 and 0.35 g/g OM after 24 h incubation with Belgian or Cuban sheep inoculum, respectively. This could - at least partially - be related to L-mimosine, present in L. leucocephala, which was hardly degraded in the Belgian incubation, while a more extensive ruminal breakdown was observed under the Cuban conditions. The negative effect of L-mimosine on OM degradability was supported in an additional in vitro experiment with straw and inoculum from Belgian sheep, as ruminal degradation of straw was 31% lower when pure L-mimosine was supplemented.

Resumen

En este estudio se evaluó la degradabilidad ruminal aparente in vitro de la materia orgánica (ARDOM) y los metabolitos secundarios vegetales (ARDPSM) de tres leguminosas tropicales (Mucuna pruriens, Canavalia ensiformis y Leucaena leucocephala). Para esto, se establecieron 3 experimentos, es decir, incubaciones de punto final único (24 h) con inóculo ruminal de ovejas belgas o cubanas, así como evaluaciones cinéticas con inóculo de oveja belga. La L-mimosina, la L-canavanina, la concanavalina A (Con A) y el inhibidor de tripsina (TI) fueron los metabolitos secundarios de la planta (PSM) objetivo de este estudio. En los tres experimentos, tanto el frijol como el forraje/harina de frijol de M. pruriens y C. ensiformis y su PSM se degradaron ampliamente durante 24 h de incubación, independientemente de la fuente de inóculo. La harina de forraje de L. leucocephala se degradó considerablemente menos, con degradabilidades ruminales aparentes de 0,20 y 0,35 g/g MO después de 24 h de incubación con inóculo de ovejas belgas o cubanas, respectivamente. Esto podría, al menos parcialmente, estar relacionado con la L-mimosina, presente en L. leucocephala, que apenas se degradó en la incubación belga, mientras que se observó una descomposición ruminal más extensa en las condiciones cubanas. El efecto negativo de la L-mimosina sobre la degradabilidad de la MO se confirmó en un experimento in vitro adicional con paja e inóculo de ovejas belgas, ya que la degradación ruminal de la paja fue un 31 % menor cuando se complementó con L-mimosina pura.