Wool follicle development in the New Zealand Romney and N type sheep. V. The pre-natal relationships between growth, skin expansion, and primary follicle number

Abstract

A method is presented for estimating changes in primary follicle number on different regions of the body of the sheep foetus from linear growth measurements and primary follicle density determinations. The major factor controlling the initiation of new primary follicle anlagen on different regions is shown to be rate of skin expansion, and therefore it appears probable that there is a competition effect between anlagen during this phase of development. After allowance is made for area increases, there are still real differences between regions in the rates of initiation of primary anlagen. There is also evidence that, during the period of primary anlagen initiation, foetuses with a greater surface area have a greater total number of primary anlagen.