Published online by Cambridge University Press: 02 September 2010
The effect of long-term treatment of goats with methylthiouracil on the timing, amount and quality of secondary fibre (cashmere) growth and timing of cashmere moult in goats was investigated. From early June, groups of 10 Icelandic × Scottish feral goats were dosed orally each day, for a 15-month period, with 5 mg methylthiouracil per kg live weight in 30 ml water (treated; T) or with water only (control; C). Treatment with methylthiouracil resulted in a significant reduction (P < 0·05) in the proportion of active secondary hair follicles present during March. This was associated with a delayed onset of moult of cashmere in T compared with C goats at both the head (11 March v. 23 February; s.e. 3·33 days; P< 0·05) and mid side (27 March v. 26 February; s.e. 3·58 days; P < 0·001). There was no effect on the time of onset (C, 19 July; T, 19 July; s.e. 5·84 days) or cessation of cashmere fibre growth (C, 9 December; T, 8 December; s.e. 1·69 days) or the mean growth rate (C, 0·473 mm/day; T, 0·451 mm/day; s.e. 0·025) and fibre diameter (C, 16·9 μm; T, 15·4 jim; s.e. 0·266). Wlien present in the fleece, the mean weight and proportion of cashmere was higher in C than in T goats (P < 0·05). It is concluded that methylthiouracil treatment altered secondary follicle activity and the time of onset of the moult of cashmere and that these changes may be a result of reduced triiodothyronine production from thyroxine and associated secondary changes in profiles of insulin and IGF-1.