Abstract
Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.Leucaena leucocephala became naturalized in Paraguay long ago. However, due to cases of toxicity in horses and cattle, now identified as mimosine toxicity, leucaena was considered a weed until the beginning of this millennium. At this time the mimosine toxicity problem was overcome by the introduction of ruminal fluid from Australia containing the mimosine-degrading and -detoxifying bacterium Synergistes jonesii. As long as an internationally funded technical assistance project was operating (offering technical advice, provision of seed, seed scarification service and transmission of ruminal fluid containing Synergistes), the area sown to leucaena (either in twin rows into grass pastures or as fodder banks) increased rapidly in Paraguay, particularly in the Chaco area. However, the powdery fluvisols of the drier parts of the Chaco were not well suited to growth of leucaena, as persistence was restricted due to the impact of rodents, termites and also leaf-cutting ants, which prosper particularly well in this part of the Chaco. In more humid areas with usually heavier soils, currently leucaena represents an integral part of the feeding systems in hundreds of Paraguayan farms (large-scale as well as smallholders), mainly for steer fattening and dairy cow supplementation. After taking into account the above-mentioned setbacks, the total area of leucaena is currently estimated at about 10,000 ha.
Highlights
The leguminous forage shrub Leucaena leucocephala is not native to Paraguay; having been introduced a long time ago it has been partly naturalized
In more humid areas with usually heavier soils, currently leucaena represents an integral part of the feeding systems in hundreds of Paraguayan farms, mainly for steer fattening and dairy cow supplementation
After some animal-to-animal transmission tests of the mimosine-degrading capability of the rumen fluid we offered a service for ruminal fluid transmission to farm animals grazing on leucaena
Summary
The leguminous forage shrub Leucaena leucocephala is not native to Paraguay; having been introduced a long time ago it has been partly naturalized. There was a major effort during the 1970s to grow leucaena on a broad scale for grazing and feeding purposes and to integrate this excellent forage, namedtropical alfalfa, into local feeding systems. These efforts failed and farmers had a generally poor image of leucaena. In studies over longer grazing periods, monthly bodyweight gains in steers decreased progressively, with weight losses being experienced after animals grazed leucaena for approximately 6 months (Klassen 2005) (Figure 1). It became obvious that a solution to this problem was crucial if wider acceptance of leucaena as a forage crop at farm level was to be achieved
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