Radiographic method for anatomic study of the teat canal: changes between milking periods.

Radiographs of the teat canal (papillary duct) of 14 Holstein-Friesian cows were made immediately after removal of the milking machine and at 2, 4, 6, and 8 hours. The distal, middle, and proximal diameters of the canal were dilated when the machine was removed. The distal and the middle parts of the teat canal were more dilated than the proximal part of the canal. Two hours later, the canal was constricted in the 3 areas. During the next 6 hours, the canal dilated-the greatest kilation being at the proximal paet of the teat canal. The average lenght of the teat canal remained unchanged. Apparently, microorganisms can easily pass through the teat canal when it is dilated at the end of machine milking and for up to 2 hours after milking.