The hair follicle population of cattle in relation to breed and body weight

Abstract

Hair follicle densities were studied in 330 cows sampled once, and 460 calves sampled twice at different ages. The calves were sampled at times varying in 2-month steps between birth and 22 months of age. Follicle density on the midside decreased with increasing body weight within animals according to a power of body weight very close to two-thirds. It is shown that data on follicle density, even from animals in the same environment sampled at the same age, are of little comparative value because of differences in body weight. Furthermore, rankings made at one age will differ from rankings at another age because of differences in growth rate. Follicle number, a figure proportional to the theoretical total number of follicles, permits valid comparisons.

Male calves had higher follicle number than female calves. Africander crossbreds were no different from Herefords and Shorthorns, but Brahman crossbreds were 20% higher in follicle number.

Individual animals of the same breed and sex differed significantly in follicle number, for which heritability was estimated at 29%. Between animals, follicle number was positively correlated with body weight. The significance and possible utility of follicle number as an indication of a component of body size is discussed.