Effects of Vacuum Level and Milking Duration on Udder Health in Mastitis-free First Calf Heifers

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Abstract
Three Jersey and 9 Holstein first-calf heifers, free from mastitis for the first 4 weeks postpartum, were milked at 10, 13 or 17 in. of vacuum from the 5th through the 44th week of lactation. Each half of each cow''s udder was milked at its designated duration on normal or twice normal for the entire comparison period. Log of the leucocyte count, chloride and pH values, and freedom from mastitis organisms in twice-weekly quarter samples showed no significant differences in avg. response among vacuum levels. Neither were differences observed for teat erosions or udder fibrosis. Time trends for leucocyte and Cl values did not differ significantly for vacuum levels, which, in fact, differed only in their tendency to curvature for the pH criterion. Halves milked for the normal duration had significantly greater mean leucocyte and Cl values and a greater linear rate of increase over the lactation for these 2 criteria and for pH than did halves milked for the twice normal duration. No significant differences were observed between milking durations for freedom from organisms, teat erosions, or udder fibrosis.