An outbreak of liver disease which killed more than 30 dogs at Alice Springs was associated with feeding meat from horses, some of which had developed Indigofera linnaei poisoning (Birdsville horse disease). Affected livers were small, nodular and yellow. There was associated jaundice, ascites, elevation of alanine aminotransferase levels in serum, a tendency to bleed, and signs of hepatic encephalopathy. Histologically, livers showed periacinar necrosis, collapse and haemorrhage, with severe swelling, vacuolation and cholestasis in remaining hepatocytes. Indospicine, a toxic amino acid found in the genus Indigofera, was detected in samples of suspect horsemeat. Experimental feeding of horsemeat containing 16 mg indospicine/kg for 32 days produced periacinar necrosis and hepatocellular swelling in 2 dogs, although neither died nor showed clinical illness. In another experiment, intakes of as little as 0.13 mg indospicine/kg bodyweight/day for 70 days produced periacinar liver lesions, and indospicine concentrations in serum, muscle and liver rose during this period to 3.9, 7.9 and 17.5 mg/kg, respectively. It was concluded that meat from horses grazing I. linnaei can be hepatotoxic for dogs, and that this toxicity may be related to its indospicine content.

SummaryIndospicine (L-2-amino-6-amidinohexanoic acid) has been newly characterized as a component of a higher plant, being isolated from the leaves and seeds of Indigofera 8picata. Indospicine was hydrolysed in distilled water at 120°C to 2-aminopimelamic acid and ammonia (1 mole). Mild acid hydrolysis of the latter compound yielded optically pure L-oc-aminopimelic acid. The infrared, nuclear magnetic resonance, and mass spectra of indospicine and of its degradation products supported the proposed structure.When injected subcutaneously into mice (1 mg/g body weight) indospicine produced fat accumulation and cytologioal ohanges in the liver. The fat aocumulation was inhibited by simultaneous injeotion of arginine but not by oanavanine. A substantial part of the hepatotoxioity of extracts of 1. 8picata seed was accounted for in terms of indospicine. The ooncentration of indospicine in the seeds exoeeded that in the leaves and stems of the plant.

Sheep on a sole diet of Leucaena glauca Benth. shed their fleece. The amino acid mimosine has been shown to be the depilatory agent. The depilatory effect of L. glauca was influenced by level and method of feeding.Small quantities of mimosine were excreted by sheep consuming L. glauca, but the major metabolite in the urine was identified as 3,4-dihydroxypyridine (DHP). It was established from the results of intravenous, intra-abomasal, and intraruminal administration of mimosine that sheep cannot detoxicate mimosine after absorption, but extensive degradation of mimosine to DHP takes place in the rumen.The absence of toxic symptoms in a sheep conditioned to L. glauca appeared to be due to increased detoxication in the rumen rather than to the development of an adaptive tolerance after absorption.The histological changes in the skin are described, and reasons for conflicting reports on the toxicity of L. glauca are discussed.A simple method for the isolation of mimosine from the seed of L. glauca is described in the Appendix.The possibility that Leucaena glauca Benth., a tropical leguminous shrub, could make a substantial contribution to the protein requirements of cattle over large areas of tropical Australia has led to an intensive research programme being carried out on this legume at the Division of Tropical Pastures, Brisbane. Hutton and Gray (1959) have stated that the reported toxicity of L. glauca to animals may be a problem in its utilization as a forage crop. Owen (1958) has summarized the extensive literature on the depilatory and other toxic effects resulting from ingestion of L. glauca leaves and seeds by ruminants and non-ruminants. Various investigators (see Owen 1958) have shown conclusively that these adverse effects in horses, pigs, and small laboratory animals were caused by the amino acid mimosine, which occurs in both the leaves and the seeds of L. glauca. The chemistry of mimosine, which has the structure P-[N-(3-hydroxy-4-pyridone)) a-aminopropionic acid, has been reviewed by Wibaut (1953).Published evidence on the toxicity of L. glauca to ruminants is conflicting. Takahashi and Ripperton (1949) and Hutton and Gray (1959) reported that beef and dairy cattle showed no toxic effects when fed on L. glauca, except in rare cases

No abstract

Lack of information on the feeding value and on the presence of deleterious substances in many species belonging to the genus Indigofera has limited the potential use of these species as feed and fodder legumes. To obtain such information, leaves and seeds of 46 accessions representing 19 species of Indigofera that had shown some agronomic value were incorporated into a semi-synthetic diet at 5% w/w (seed) or 20% w/w (forage). The diets were fed to groups of young rats for 4 weeks, and dry matter intakes and growth rates relative to control diets were measured. Selected organs were examined for any histological changes. Seed and forage samples were analysed for indospicine, a hepatotoxin, and for the presence of another potentially deleterious substance, 3-nitropropanoic acid. Thirteen of the accessions representing 8 species were readily eaten and did not depress growth rates relative to control feeds, and another 13 representing 10 species gave acceptable growth rates. Liveweight gains were less affected by forage diets than by those containing seeds. With the exception of those in rats fed on diets containing I. spicata and I. nigritana, the organs of all other rats were histologically normal. It is unlikely that the concentration of 3-nitropropanoic acid (0.5-3.4 mg g-1 dry matter) in any feed was high enough to cause any of the observed toxic signs. Indospicine was present in only 4 of the 23 species tested, including all accessions of I. spicata, and the concentration of indospicine was a good indicator of the toxicity of these feeds. It is concluded that accessions that had produced growth rates comparable to those of controls may be recommended as non-toxic feeds suitable for further testing.