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Prolonged consumption of Indigofera pasture plants can cause both hepatotoxicosis and reproductive losses in grazing animals with the responsible toxin indospicine forming persistent tissue residues. Separate accumulation and depletion feeding trials were undertaken in calves fed Indigofera spicata (3 mg indospicine/kg bodyweight) to ascertain the appearance and elimination of indospicine from various tissues. In the accumulation trial indospicine concentrations increased throughout the 42-day feeding period with maximum levels of 15 mg/L in plasma and 19 and 33 mg/kg in liver and muscle, respectively. In the depletion trial, calves were fed I. spicata for 35 days, after which the plant was withdrawn from the diet. The rate of elimination was relatively slow with estimates of half-life being 31, 25 and 20 days for muscle, liver and plasma, respectively. Indospicine levels measured in bovine tissues in this trial are comparable with levels in horsemeat and camel meat reported to cause fatal hepatoxicity in dogs, a species known to be susceptible to this toxin. The persistence of indospicine residues in bovine tissues and the widespread distribution of Indigofera species in tropical and sub-tropical grazing lands warrant further investigation, as indospicine has been established as causing reproductive losses and likely contributes to calf losses in these regions.

Further proof is offered that the toxic constituent of creeping indigo is β-nitropropionic acid. This compound was synthesized and compared with the isolated material. Both compounds were toxic in the chick test, both had the same melting point, and both gave the same infrared absorption spectra. A sensitive chemical test for the quantitative analysis of this compound in plant material is discussed. This test is sufficiently sensitive so that individual plants may be tested for the presence of this toxic compound. A survey of the nitrogen compounds in creeping indigo revealed a high nitrite concentration. Nitrites were shown to be relatively toxic in the chick test and so may add to the toxicity of creeping indigo.

(1950). The Effect Of Creeping Indigo (Indigofera Endecaphylla) When Fed To Growing Chickens. World's Poultry Science Journal: Vol. 6, No. 4, pp. 284-291.