Characteristics of a Rumen Clostridium Capable of Degrading Mimosine, 3(OH)-4-(1H)-Pyridone and 2,3 Dihydroxypyridine

Performance, Rumen Microbial Community and Immune Status of Goat Kids Fed Leucaena leucocephala Post-weaning as Affected by Prenatal and Early Life Nutritional Interventions

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.

Isolation and characterization of mimosine, 3, 4 DHP and 2, 3 DHP degrading bacteria from a commercial rumen inoculum

The presence of the toxic amino acid mimosine in Leucaena leucocephala restricts its use as a protein source for ruminants. Rumen bacteria degrade mimosine to 3,4- and 2,3-dihydroxypyridine (DHP), which remain toxic. Synergistes jonesii is believed to be the main bacterium responsible for degradation of these toxic compounds but other bacteria may also be involved. In this study, a commercial inoculum provided by the Queensland's Department of Agriculture, Fisheries, and Forestry was screened for isolation and characterization of mimosine, 3,4- and 2,3-DHP degrading bacterial strains. A new medium for screening of 2,3-DHP degrading bacteria was developed. Molecular and biochemical approaches used in this study revealed four bacterial isolates - Streptococcus lutetiensis, Clostridium butyricum, Lactobacillus vitulinus, and Butyrivibrio fibrisolvens - to be able to completely degrade mimosine within 7 days of incubation. It was also observed that C. butyricum and L. vitulinus were able to partially degrade 2,3-DHP within 12 days of incubation, while S. lutetiensis, was able to fully degrade both 3,4 and 2,3 DHP. Collectively, we concluded that S. jonesii is not the sole bacterium responsible for detoxification of Leucaena. Comprehensive screening of rumen fluid of cattle grazing on Leucaena pastures is needed to identify additional mimosine-detoxifying bacteria and contribute to development of more effective inoculums to be used by farmers against Leucaena toxicity.

Efficacy, persistence and presence of Synergistes jonesii in cattle grazing leucaena in Queensland: on-farm observations pre- and post-inoculation

A study of eight commercial cattle herds grazing leucaena (Leucaena leucocephala subsp. glabrata) pastures was undertaken to determine (1) the efficacy of in vitro Synergistes jonesii inoculum (produced in an anaerobic fermenter) in degrading the dihydroxypyridone (DHP) isomers produced during digestion of leucaena forage; and (2) the persistence of the inoculum in the rumen of cattle following a period grazing non-leucaena pastures. Cattle were introduced to the leucaena pastures for an initial period varying from 17 to 71 days. Fourteen to fifteen animals were then sampled for (1) urine and blood plasma to determine toxicity status as indicated by concentration of DHP; (2) faeces for estimation of diet composition; and (3) rumen fluid for detection of S. jonesii by nested polymerase PCR analysis. After a further 42–56 days, animals were resampled as before to confirm toxicity status and inoculated with the in vitro S. jonesii inoculum; the herds were then sampled a third time (42–60 days after inoculation) to test the effectiveness of the inoculum in degrading DHP. Five of the herds were then removed from leucaena pastures for periods ranging from 80 to 120 days and returned to leucaena pastures for 21 days to check persistence of the inoculum as indicated by retention of capacity to degrade DHP. The data indicated (1) a very slow build up of capacity to degrade DHP isomers on some properties before inoculation; (2) frequent occurrence of high levels of 2,3-DHP in urine indicating partial toxin degradation, both before and after inoculation; (3) a low incidence of detection of S. jonesii in rumen fluid after inoculation based on nested PCR analysis; (4) failure of inoculation to degrade DHP on one of two properties tested; and (5) loss of capacity to degrade DHP on some properties after <4 months on alternative non-leucaena pastures. It was concluded that while most herds showed some capability to degrade DHP due to some residual capability from previous exposure, they did not achieve the same rapid and complete DHP degradation reported in the 1980s. Nevertheless, it was concluded that the in vitro inoculum was at least partially effective and should continue to be used by graziers until improved sources of inoculum and/or inoculation methodologies are demonstrated.