The medullation characteristic of the hair coat as a factor in heat tolerance of cattle

Abstract

Measurements of the hair fibres of the cattle coat show, besides considerable seasonal variation in the length, diameter, and weight of hair per unit area, marked changes in the incidence and degree of medullation, which may account for the required variation in the thermal effect of piliary development associated with seasonal conditions. The medulla, a structural component of the hair fibre, may be a critical characteristic of the coat in the regulation of heat dissipation by the animal. The correlation between the incidence of medullation and the animal's ability to regulate the rectal temperature was 0.95.