The variability оf hair dysplasia dynamics as possible index of adaptation level of sheep to their breeding conditions

Abstract

The dynamics of hair diameter of different sheep breeds and populations in Eastern, Central and Southern Kazakhstan was investigated to test the possibility of estimation of sheep adaptation to real breeding environment basing on their hair condition. The lanometric scanning of the hairs from their distal to proximal ends was accomplished which correspond to their growth period from the spring shearing up to later April of the next year. Hair diameters dropped down averagely to 78% of their maximal level when the optimal season (summer) was changed for unfavorable one (winter, early spring) with its stress caused by cold weather, worse nutrition, short day. This hair dysplasia is accompanied by ceasing of hair medulla differentiation. Rather wide individual variability of stress-induced hair dysplasia was detected within the same herd, the difference between maximal and minimal hair diameters varying from as low as 9% up to 46%. This variability may be used in sheep selection for resistance against unfavorable season factors.