Machine milking–induced alterations of teat tissue may impair local defense
mechanisms and increase the risk of new intramammary infections. The objective
of the current study was to assess the influence of short-term and long-term
alterations of teat tissue and infectious status of the udder quarter on the
risk of naturally occurring new intramammary infections, inflammatory
responses, and mastitis. Short-term and long-term changes in teat condition of
right udder quarters of 135 cows of a commercial dairy farm in Saxony-Anhalt,
Germany, were recorded monthly for 10 mo using simple classification schemes.
Quarter milk samples were collected from all examined quarters at each farm
visit. Bacteriological culture results and somatic cell counts of quarter milk
samples were used to determine new inflammatory responses (increase from
≤100,000 cells/mL to >100,000 cells/mL between 2 samples), new infections
(detection of a pathogen from a quarter that was free of the same pathogen at
the preceding sampling), and new mastitis (combination of new inflammatory
response and new infection). Separate Poisson mixed models for new
inflammatory responses, new infections, and new mastitis caused by specific
pathogens or groups of pathogens (contagious, environmental, major, minor, or
any) were used to estimate risk ratios and 95% confidence intervals. Data
preparation and parameter estimation were performed using the open source
statistical analysis software R. We observed no effect of any variable
describing teat condition on the risk of new intramammary infections,
inflammatory responses, or mastitis. Intramammary infections of the same udder
quarter in the preceding month did not affect risk either