Changes in wool growth and the skin of Merino sheep following administration of cyclophosphamide

Abstract

Two Merino sheep were dosed orally, and two intravenously, with cyclophosphamide at the rate of 30 mg/kg body weight; the effects on wool growth were measured, and changes in the histology of skin and of wool follicles were studied.

All sheep were readily defleeced following treatment. This effect was associated with a complete cessation of wool growth for a period of about 2 weeks with oral dosing and 2½ weeks with intravenous dosing. There was considerable variation in the time taken for new fibres to commence growth. Length growth rates during the period 28–36 days after dosing were consistently greater than pre-treatment rates. Post-treatment fibre diameters were variable compared with the pretreatment values. The extent to which the enhanced length growth after dosing would compensate for the loss of wool growth requires further investigation.

Degenerative changes were observed in some wool follicles 1 hr after dosing, and proliferation of cells of the fibre and inner root sheath appeared to have ceased at 1 day. Fibre growth ceased prior to 4 days. Regeneration of most follicles commenced prior to 14 days after dosing, and regrowth of wool was apparent above the skin by 21 days. A small proportion of follicles was still inactive after 36 days.

Changes were observed in the sebaceous and sweat glands, epidermis and dermis following dosing. Even 36 days after dosing, sebaceous glands were considerably enlarged and excess stratum corneum remained on the epidermis. Infiltration of the dermis by lymphocytes was observed as early as 1 hr after dosing and was intense by 28 days.