Overcoming Leucaena's toxicity
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CTA. 1987. Overcoming Leucaena's toxicity. Spore 7. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/44582
The leguminous tree Leucaena leucocephala could now be heading for much wider use, thanks to the development of a practical method of avoiding its toxic effects when fed in large quantities to ruminants. Its protein-rich leaves are highly palatable...
The leguminous tree Leucaena leucocephala could now be heading for much wider use, thanks to the development of a practical method of avoiding its toxic effects when fed in large quantities to ruminants. Its protein-rich leaves are highly palatable to cattle and goats; in spite of the presence of mimosine, a toxic amino acid, they can tolerate a diet of up to 30 % leucaena, because of their ability to break down the mimosine to a less toxic substance, DHP. However. when diets exceed this level, DHP interferes with the thyroid's ability to incorporate iodine, this leads to listlessness, loss of appetite and weight loss. It was discovered in Indonesia that some goats and cattle can completely degrade DHP and are apparently able to transfer this ability to other animals through saliva left on shared food. There have been conflicting reports from Hawaii and elsewhere on the subject. A hypothesis that Australian cattle suffered from mimosine toxicity because they lacked DHP-degrading bacteria was substantiated by research workers at the Commonwealth Scientific and Industrial Research Organization (CSIRO) by transferring rumen bacteria from Indonesian to Australian goats. They then showed the bacteria could be cultured in vitro. Following these discoveries rumen fluid from a Hawaiian goat has been used to provide inoculum for use in field experiments in Australia. Successful results have now been reported from a number of trials. In one leucaena grazing experiment 20 cattle inoculated with a culture of DHPdegrading bacteria stopped excreting DHP in their urine and their blood serum thyroxine levels remained normal. However 20 heifers grazing in simiia; conditions, but not inoculated with the bacteria, excreted DHP in their urine and had extremely low levels of thyroxine in their blood In another experiment, an inoculated steer and four control steers were grazed on a leucaena-based pasture. Within five weeks, it was clear that the ability to break down DHP had been transferred from the inoculated steers to the four others. According to the CSIRO scientists, preliminary evidence indicates that the detoxifying bacteria became established in treated animals. Over a year after being inoculated, the initial experimental animals have retained the bacteria. There are good reasons for believing that a practical solution to the problem of leucaena toxicity is in sight. For further information consult: IDRC Report July 1985 P O Box 8500 Ottawa CANADA K1G 3H9