01868naa a2200253 a 450000100080000000500110000800800410001910000210006024501530008126000090023452011000024365000190134365000190136265000100138165000230139165000210141465000120143565000220144765000130146965300260148265300150150870000170152377300740154015308592023-06-30       1983    bl uuuu     u00u1 u    #d1 aMEGARRITY, R. G.  aToxicity of Leucaena leucocephala in ruminantsbthe effect of supplemental thyroxine on goats fed on a sole diet of Leucaena.h[electronic resource]  c1983  aAbstract: Daily injections of thyroxine were ineffective in overcoming the toxic effects of feeding Leucaena to goats. The treated goats did not differ from the controls in liveweight change or body condition over the 15 weeks of feeding Leucaena and both groups of animals developed oesophageal lesions. Treated animals maintained normal serum thyroxine (T4) and triiodothyronine (T3) levels and did not exhibit the thyroid hyperplasia of the controls. An increase in the serum T4 and T3 levels of three of the control animals after 5 weeks of feeding was associated with declining mimosine concentration in the feed and the ability of the hyperplastic thyroids to produce sufficient T4. Serum analyses suggested zinc deficiency in the control animals, associated with their low thyroid status. It was concluded that the goitrogenicity of 3-hydroxy-4(1H)-pyridone (DHP) is only partly responsible for the toxicity of Leucaena to ruminants, and that the low feed intakes and low liveweight gains are related to other effects of DHP. The evidence for extra-ruminal metabolism of DHP is discussed.  aAnimal feeding  aForage legumes  aGoats  aRuminant nutrition  aToxic substances  aCaprino  aNutrição Animal  aTiroxina  aLeucaena leucocephapa  aToxicidade1 aJONES, R. J.  tAustralian Journal of Agricultural Researchgv. 34, p. 791-798, 1983.