Effects of Methoxinine, an Analogue of Methionine, on the Growth and Morphology of Wool Fibres

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Abstract
Methoxinine (O-methyl-DL-homoserine) was given to 18 Merino sheep by intravenous infusion or injection in amounts of 52-100 mg/kg body weight. Effects on strength, morphology and growth rate of wool fibres were studied. On average, methoxinine reduced the strength of bundles of wool fibres to about one-third of pretreatment values, but the magnitude of the effect varied considerably between sheep. Methoxinine also reduced the staple crimp frequency over a distance of c. 5-30 mm. A loss of cuticle scale pattern on wool fibres was observed following dosing; other abnormalities included grooved cuticle scales, degraded sections of fibre and distorted fibres. Wool growth was temporarily reduced after methoxinine administration to c. 60% of the pretreatment rate. Effects were greater and more rapid on length growth rate than on fibre diameter. None of the above effects of methoxinine was prevented by the concurrent administration of cysteine and the efficacy of the concurrent administration of methionine was equivocal. A continuation of the infusion of methionine for 4 weeks following methoxinine administration prevented the depression of wool growth and either prevented or reduced the effects on wool fibres. Following a dose of methoxinine (60 mg/kg) the concentration of methoxinine in blood plasma was 500-800 .mu.mol/l, at the end of a 2-day infusion or 5 h after an injection. The concentration in plasma declined slowly thereafter and was 50-80 .mu.mol/l after 5 weeks. The effects of methoxinine were not mediated via copper deficiency as judged by plasma copper concentrations and the failure to cause depigmentation of black wool.

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