Histopathology of Hypotrichosis in Calves

Abstract

SummaryThe histopathology of the skin in hypotrichosis has been studied for a Jersey calf and comparisons made with normal skin. Other abnormalities of the hair follicle have been described in a Hereford mutant.There is considerable variation in hypotrichosis of the calf, as in mice, all forms involving retardation or arrest of the prenatal and early postnatal skin development.A feature of the skin in hypotrichosis is a high concentration of abnormally complex arteriovenous anastomoses. It is postulated that this abnormality of cutaneous vascular supply is a predisposing factor in the development of the syndrome. The poor development of the hair follicles and associated sweat glands appears to result from insufficiency of the capillary bed. An analogous situation in humans is cutaneous necrosis of the leg as a result of dilatation of the arteriovenous anastomoses.While arteriovenous anastomoses do not appear compensatory to lack of sweat glands, they do provide an alternative thermoregulatory mechanism which might be effective at moderate environmental temperature.

Factors Determining Sweating Competence of Cattle Skin

“…Within skin areas of approximately 10 cm2, smaller subareas can be defined which may differ in sweating rate by as much as 300%. This difference is as great as or greater than that reported between different body regions (McLean 1963;Pan, Donegan, and Hayman 1969) and between different seasons (Schleger and Turner 1965). The sweating pattern is most marked when the coat is longest and follicle activity and sweating rate least.…”

“…The state of activity of the hair follicles would appear to be of prime importance. Exhaustive studies have shown that sweat gland size varies with each phase of the hair growth cycle (Schleger, unpublished data), although at no times does it approach zero as previously reported (Schleger 1966). The effect of hair growth phase on the capillary supply to the sweat gland is far more critical than its effect on sweat gland size and appears to be a limiting factor in sweat gland performance.…”

“…The close relationship between blood supply and follicle activity in the rat and rabbit has been described by Durward and Rudall (1958), while its relevance to hypotrichosis in calves has been pointed out by Schleger, Thompson, and Hewetson (1967). The reduced physiological activity of sweat glands with old age in man is thought to be dependent on a decrease in blood supply and degeneration of the nervous control mechanism (Mackinnon 1954).…”

“…Observations of sweating rate at different times of the year (Schleger and Turner 1965) have demonstrated the seasonal nature of sweating competence, maximum sweating rates being significantly lower in winter than summer. When coat score and sweating rate were determined at the one time, the type of coat was associated with capacity to sweat.…”

An overview on congenital alopecia in domestic animals

“…Viable hypotrichosis has been described in the Guernsey, Jersey, Holstein, and Hereford breeds. [111][112][113][114][115] It is inherited as an autosomal recessive trait and is characterized by generalized congenital alopecia, with sparse hair on legs, tail, eyelids, and ear pinnae. Histopathology reveals dysplastic hair follicles that do not produce hair shafts.…”