INFLUENCE OF PULSATIONLESS MILKING ON TEAT CANAL KERATIN AND MASTITIS

Twenty-four Holstein cows, producing at least 21 kg of milk/d, were us ed in two replicate experiments to determine the effect of presence or absence of pulsation on loss of teat canal keratin during machine mil king. Left quarters were milked without pulsation and right quarters w ere milked with pulsation. On d 0 and 10, keratin was collected from o ne 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 approximat ely 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 pul sation had become infected, but no (0 of 47) quarters milked with puls ation 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 inc reased sevenfold relative to pulsation quarters. Protein and water con tent of keratin did not differ because of treatment, and changes in li pid composition were minor. Histological analysis of the teats of 4 co ws indicated that the mean diameter of the teat canal, within 2 h afte r milking, was greater without pulsation than with pulsation (680 vs. 483 mum).