D. PRATCHETT¹, R.J. JONES² and F.X. SYRCH³

¹Western Australian Department of Agriculture, Kununurra, W.A.;
²Division of Tropical Crops and Pastures, CSIRO, Townsville, QLD and
³CSIRO, Kununurra, W.A.; Australia.

Abstract

Leucaena toxicity in cattle in the Ord River Irrigation Area has been severe due to high mimosine concentrations over most of the year. Control of mimosine toxicity was achieved by dosing heifers with rumen fluid containing bacteria which are capable of degrading 3-hydroxy-4(1H)-pyridone (DHP).
Two groups of yearling Shorthorn heifers were grazed on, irrigated leucaena-pangola pastures. Heifers in one group were each given an oral dose of DHP-degrading bacteria. Heifers in the other group were used as controls. Groups were separated by 4 ha of ungrazed verano-pangola pasture.
Within 4 weeks of dosing, excretion of DHP in the urine of treated heifers almost ceased, serum thyroxine levels returned to normal and clinical signs of toxicity were absent. Dosed heifers were 15 kg heavier (P < 0.01) than the controls after 12 weeks.
By the 12th week after dosing, the bacteria had spread to the control group and those heifers then recovered from the toxicity and overall weight gains 20 weeks after dosing were similar to the dosed group. Four calves born to heifers in the control group were found dead, while 3 calves born in the treated group were normal.