Seasonal variation in hair follicle activity and fibre growth of both male and female Merghoz goats in Western Iran

Ten female and 10 male Merghoz goats with initial liveweights of 24.02 ± 1.7 and 29.2 ± 1.2 kg (mean ± s.e.) respectively were used to investigate the effect of naturally changes in photoperiod on hair follicle activity and fibre growth in a 365 day study. The animals were housed in individual pens, under natural day length condition at west of Iran, Kermanshah (34°18′N and 47°3′E and 1420 m above sea level). A diet was offered with an estimated concentration of metabolizable energy and crude protein of 7.9 MJ and 98.8 g/kg DM respectively. Follicular density (FD), percentage of active primary and secondary follicles (PAP and PAS) and ratio of secondary to primary follicles (S/P) were determined from skin biopsies, taken from the right mid-side of the goats every one month. Clean fibre yield and fibre diameter were measured from mid-side patches harvested at the end of every month after morning feeding. Dry matter intake (DMI) and average daily gain (ADG) displayed a substantial seasonal variation. There was a significant effect (p < 0.001) of season on PAP and PAS (primary: 98.0, 74.1, 45.9 and 89.0%; secondary: 99.0, 80.9, 70.6 and 92.5%; for summer, autumn, winter and spring, respectively) but, no seasonal differences were observed in FD and S/P. Seasonal differences in clean fibre yield and fibre diameter patterned those of follicle activity. There was a season × sex interaction on both fibre growth rate and fibre diameter. It is concluded that seasonal cycles of feed intake, growth, hair follicle activity and fibre growth may occur in goats.