ULTRASTRUCTURAL OBSERVATIONS ON BOVINE TEAT DUCT

Ultrastructural studies were made on the teat ducts of cattle of various ages and milking status, cattle with clinical masititis and cattle which had been inoculated into the teat duct with staphylococci. The structure of the bovine teat duct was consistent with its formation from the outer integument. Specialisations of cell connections across the intercellular spaces of the basal epidermal cells suggested an adaptation for expansion and contraction relevant to sphincter function. The keratin layer appeared to be derived from units of cells of epidermal origin and no evidence of a specific secretion was seen in material prepared by the methods used. It is suggested that any components in the keratin having antibacterial activity were derived from epidermal cells. The mesh-like nature of the keratin was such as to reduce the rate of progress of any cocci en route from the teat orifice to the mammary gland, but this would not preclude the operation of other defence mechanisms such as antibacterial substances. There was little evidence of differences in structure of the teat ducts of cattle categorised for age, lactation or clinical masititis. Cocci deposited experimentally in the teat duct of a dry cow were subsequently examined in ultrathin sections. Cocci and debris were identified in the teat ducts of cases of clinical mastitis. © 1969.