Observations on hair growth and shedding in cattle

Abstract

On three occasions during the period l91S-1956 field observations were made on coat shedding in B. indicus, B. taurus, and B. indicus x B. taurus cattle, and hair and skin samples taken. Measurements of hair length, diameter, and weight per unit area of skin were made, and stages of hair growth within the follicle observed. On two occasions hair data included measurements of length and diameter on individual hairs. Two shedding periods were observed. in spring and in autumn. Approximately 4 months was required for the complete change from m-inter to summer coat, the change in appearance being dramatic. Less time was required for autumn shedding and there was a less dramatic change in the appearance of the coat. Histological data from skin samples supported these observations and showed that during shedding almost all mature hairs were lost from the skin follicles. All types of cattle had characteristically short, light summer coats and long, heavy winter coats. No difference in hair diameter was observed between summer and winter coats in B. taurus, but in B. indicus hair diameter was much greater in the summer coat. In all seasons 01 the year B. indicus had the shorter and lighter coats. The minter coat in long-coated B. tauws did not appear to hare an undercoat, whereas short-coated B. taurus and B, indicus had distinct undercoats. In B. indicus x B. taurus F1 crossbreds coats were as'short in summer as those of B. indicus, and as long in winter as those of B. taurus. Differences between species in shedding, and in coat characteristics at different seasons of the year, may be of ecological importance.

A field study of coat shedding in cattle under conditions of equal day-length but different temperatures

“…Exposure of animals from birth to a constant equatorial daylength prevented the normal seasonal shedding response (Yeates, 1957), which suggests the absence of an inherent cycle of pelage changes in cattle. Hayman & Nay (1961) suggest that the pituitary may also be responsive to decreasing day-length, in view of the occurrence of an autumn shedding. On the other hand, Johnson & Ragsdale (1960), McDowell et al (1960) and others have observed marked effects of temperature on coat changes under constant conditions of daylength.…”

Swat Glant and Hair Follicle Measurements as Indicators of Skin Type in Cattle

“…These findings are not substantiated by the present experiments in which full-sized sweat glands were observed associated with hair follicles in all stages of the hair cycle in all instances where the gland was complete and undamaged by cutting and processing. Schleger's claim is surprising because about 60% of the hair follicles in cattle are in the resting phase during the summer (Dowling and Nay 1960;Hayman and Nay 1961) and it would follow that the capacity of cattle to sweat at the warmest time of the year would be drastically reduced.…”

“…Nay and Hayman (1963) confirmed that sweat gland volume can change with season, but noted that sweat gland shape does not alter with season. Hayman and Nay (1961) and Berman and Volcani (1961) concluded that hair fibre diameter can be larger in summer than in winter in tropical cattle although the former authors failed to find a difference in this parameter in European cattle. Hair length also varies with season.…”

“…Resting hair follicles, although present in the skin sections, were not measured. Giant follicles seated deep in the reticular layer and representing 4-6% of the total amount present (Hayman and Nay 1961) were ignored. Depths of each of lO follicles in each section were measured and the mean value taken as the typical follicle depth.…”

Relationship Between Cyclic Changes in the Hair Follicle and Sweat Gland Size in Cattle

“…In regard to seasonal differences in sweating capacity, Dowling and Nay (1960) and Hayman and Nay (1961) showed that the winter coat contains a higher proportion of club hairs, representing catagen and telogen phases, than the summer coat. The high proportion of club hairs in winter would mean a high proportion of glands in proximity to the regressed catagen a and telogen phases and this would cause a reduced sweating capacity, such as has been observed.…”