The biological basis of variation in sheep's fleece cover

摘要

Efficient sheep farming of the future will demand reduced labour costs, ease of shearing, and minimised susceptibility to flystrike, while modern markets simultaneously demand reduced chemical use and high standards of animal welfare. Sheep with a reduced area of the body covered with fleece may provide a practical solution to these conflicting requirements. Research has shown that it is possible to select sheep for bare faces, legs, belly and breech, and that at least some of these traits behave asthough they are controlled by recessive genes, but that some only become evident later in life. Patterns of fleece distribution define major skin domains in the sheep that are evident in other mammals. We hypothesise that discrete skin domains arise because fibroblasts that induce wool follicle development originate from different embryonic tissues and carry with them differing developmental programmes for each follicle type. Identifying genes underlying variation in fleece distribution would allow desirable distributions to be established in sheep of diverse genetic backgrounds. Markers for distribution traits would enable us to introgress appropriate genes into flocks that do not carry them, and to determine early in life which animals might expressthe traits as adults.