Some effects of three glucocorticoid analogues on wool growth and their efficacy as defleecing agents in sheep

Abstract

Some effects of the parenteral administration of three glucocorticoid analogues, namely Opticortenol (dexamethasone-21 -trimethylacetate), Decadron phosphate (dexamethasone-21 -phosphate) and the heterocyclic corticosteroid, Cortivazol, were observed on wool growth in sheep. None of the glucocorticoids was satisfactory for defleecing sheep, principally because of variation between sheep and between body regions in the wool growth response. Four main types of response to dosing with glucocorticoids were observed : Firstly, with some animals there was no obvious effect on wool growth. In a second category there was a well-defined 'break' in some wool fibres but the fleece as a whole was retained by other unbroken fibres. Thirdly, complete or partial shedding of the fleece was seen, unshed portions usually being present on the head, neck and shoulder regions and consisting mainly of broken wool fibres but also a proportion of whole fibres. Finally, prolonged wool growth depression without shedding of the fleece during the experimental period was also seen. Results indicated that to obtain shedding of the fleece in 15-20 days after dosage, wool growth needs to be reduced below 20 per cent of its pre-treatment values and regrowth must be rapid.