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Influence of Pulsationless Milking on Teat Canal Keratin and Mastitis

Milk Secretion and Mastitis Laboratory, Livestock and Poultry Science Institute, US Department of Agriculture, ARS, Beltsville, MD 20705 and Department of Dairy Science University of Wisconsin, Madison 53706 and Hill Farm Research Station, Louisiana State University Agricultural Center, Homer 71040

Twenty-four Holstein cows, producing at least 21 kg of milk/d, were used in two replicate experiments to determine the effect of presence or absence of pulsation on loss of teat canal keratin during machine milking. Left quarters were milked without pulsation and right quarters were milked with pulsation. On d 0 and 10, keratin was collected from one left and from one right teat canal of each cow prior to milking and from the remaining two teat canals after milking. Milk was collected for assessment of SCC and bacteriological status on d 0 and approximately every 3 d until d 18. Quantity of keratin recovered before milking on d 10 did not differ between teats milked with or without pulsation, but loss of keratin because of milking was greater from teats milked with pulsation. By d 7, 30% (12 of 43) of quarters milked without pulsation had become infected, but no (0 of 47) quarters milked with pulsation were infected. By d 14 to 16, new infections had increased to 68% (28 of 41) of quarters milked without pulsation and 2% (1 of 43) in quarters milked with pulsation; mean SCC in pulsationless quarters increased sevenfold relative to pulsation quarters. Protein and water content of keratin did not differ because of treatment, and changes in lipid composition were minor. Histological analysis of the teats of 4 cows indicated that the mean diameter of the teat canal, within 2 h after milking, was greater without pulsation than with pulsation (680 vs. 483 µm).