Leucaena leucocephala represents a local protein source in tropical ruminant diets. However, its full exploitation is impaired by mimosine, unless it is degraded by the rumen microbial community. Recently, the ruminal bacterial communities of newborns were persistently modified through prenatal or postnatal dietary interventions. Such early-life interventions might enhance adaptation of ruminants to Leucaena leucocephala, which was investigated using a 2 × 2 factorial design trial that tested both supplementation of L. leucocephala in the late pregnancy diet of goat does, and supplementation of live yeast to their newborns. The composition of ruminal bacteria, immune status, as well as organic matter digestibility (OMD) and performance of kids were studied during and after the intervention. Ten pregnant goats were divided into two groups: the D+ and D– groups, which either received or did not receive 30 g of L. leucocephala forage meal during the last 7 ± 0.5 weeks of gestation. Twins from each goat were divided into the K+ and K– group (supplemented with or without 0.2 g/d of live yeast from day 3 until weaning at 8 weeks). Rumen samples were collected from 4-, 8-, 14-, and 20-weeks old kids to assess the bacterial community, while immune parameters (white blood cells, immunoglobulin M and G, and chitotriosidase activity) were measured in blood and saliva sampled at 4-, 8-, and 20-weeks. We found a stimulatory effect of the prenatal exposure on the post-weaning dry matter intake of the L. leucocephala supplemented diet, resulting in a higher daily gain and final body weight at 20 weeks in the D+ vs. D– group (406 vs. 370 g DM/d, 85.4 vs. 78.6 g/d, and 15.2 vs. 13.8 kg, respectively). Moreover, Ruminococcus represented a greater proportion of the rumen bacterial community of the D+ vs. D– kids (5.1 vs. 1.6%). Differences in the immune status were relatively small and not thought to be a driving factor of differences in animal performance. Furthermore, postnatal supplementation of live yeast favored maturation of the rumen bacterial community (i.e., greater abundance of Bacteroidetes, in particular Prevotella, and reduced abundance of Firmicutes) and protozoa colonization. Concomitantly, OMD was enhanced post-weaning, suggesting effects of the early-life intervention persisted and could have affected animal performance.

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, single end-point incubations (24 h) as well as kinetic assessments (0, 2, 4, 6, 8, 10, 12 and 24 h) were set up with different inocula sources, i.e. ruminal inocula from Belgian and Cuban sheep. L-mimosine, L-canavanine, Concanavaline A (Con A) and trypsin inhibitor (TI) were the plant secondary metabolites (PSM) targeted in this study. Bean and forage/bean meals of M. pruriens and C. ensiformis as well as their PSM were extensively degraded during 24 h incubation (0.70 and 0.78 g ARDOM/g of organic matter (OM), respectively and > 0.80 g/g for L-canavanine, > 0.76 TIU/TIU for TI and > 0.95 g/g for Con A, for both legumes). Forage meal of L. leucocephala was considerably less degraded, with apparent ruminal degradabilities of 0.20 and 0.35 g ARDOM/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 (0.05 to 0.78 g ARDPSM/g PSM, respectively). The negative effect of L-mimosine on OM degradability was supported by in vitro incubations with straw and inoculum from Belgian sheep, as ruminal degradation of straw was 31% lower when L-mimosine was supplemented.

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, single end-point incubations (24 h) as well as kinetic assessments (0, 2, 4, 6, 8, 10, 12 and 24 h) were set up with different inocula sources, i.e. ruminal inocula from Belgian and Cuban sheep. L-mimosine, L-canavanine, Concanavaline A (Con A) and trypsin inhibitor (TI) were the plant secondary metabolites (PSM) targeted in this study. Bean and forage/bean meals of M. pruriens and C. ensiformis as well as their PSM were extensively degraded during 24 h incubation (0.70 and 0.78 g ARDOM/g of organic matter (OM), respectively and > 0.80 g/g for L-canavanine, > 0.76 TIU/TIU for TI and > 0.95 g/g for Con A, for both legumes). Forage meal of L. leucocephala was considerably less degraded, with apparent ruminal degradabilities of 0.20 and 0.35 g ARDOM/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 (0.05 to 0.78 g ARDPSM/g PSM, respectively). The negative effect of L-mimosine on OM degradability was supported by in vitro incubations with straw and inoculum from Belgian sheep, as ruminal degradation of straw was 31% lower when L-mimosine was supplemented.