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Bovine Intramammary Pressure Changes during Mechanical Milking¹

Physiopathology and Bacteriology Sections, National Animal Disease Laboratory, USDA, Ames, Iowa

ABSTRACT

Pressure changes within the intact bovine udder were measured during mechanical milking. Simultaneous pressure recordings were obtained from the teat sinus, gland sinus, pulsator line, and milk line. Indwelling polyvinyl catheters were used to obtain pressure measurements in the teat and gland sinuses. Data from 24 recordings on 12 different quarters of five cows were evaluated. Intramammary pressure increased with milk letdown and was followed by a gradual decline during milk flow. At the end of milk flow a pulsating vacuum developed in the teat sinus, and a residual teat sinus vacuum persisted after inflation collapse. A slight residual gland sinus vacuum also developed after the end of milk flow. After milk removal and teat canal ligation, residual vacuum did not develop in the teat sinus during normal milking machine operation, although a pulsating vacuum was noted. Pressure change in the teat sinus apparently resulted from inflation action upon the teat wall and extension of milk line vacuum through the teat canal.

¹ Taken, in part, from a thesis to be submitted by the senior author to the Graduate College, Iowa State University (Ames, Iowa), in partial fulfillment of the requirements for the M.S. degree in Physiology, Department of Physiology and Pharmacology, College of Veterinary Medicine.