What Percentage of Intramammary Infections
Are Caused by Milking Machine Factors?
At the 1987 International
Mastitis Symposium in Montreal, Canada, the question was asked "What
percentage of all infections are due to milking machine factors?"
The answers given were "we don't really know"; "probably quite low";
and "anywhere between 0% and 100%".
Can we provide any more definitive answers today?
Informed estimates of direct and indirect milking machine effects range
from about 6% to 20% of the overall new mastitis infection rate. The
direct effects (including bacterial transport, cross-contamination and
impacts) might account for about 10% of new infections on most farms.
Indirect effects (including effects on the health of the teat canal,
teat tissues and skin) might account for another 10% in an average herd.
However, it is difficult to go beyond these broad-brush estimates.
When reading published articles or discussing field experience, remember
that correlation does not imply causation. The world is full of testimonials
and chance correlations. Attempts to correlate single-factor effects
with poor teat condition or udder health often provide false hopes in
reaching the ultimate goals of herd health and milk quality. Thus, we
agree with the conclusion of M.W. Woolford (Proc. 3rd IDF International
Mastitis Seminar, Israel,1995) that "further quantification of the
overall contribution of the machine contribution is difficult and elusive
because of the multi-factorial nature of the disease".
Despite these elusive difficulties, it is clear that the majority of
new infections are caused by factors other than the milking machine.
Source: Milking Machines and Mastitis Risk: A Storm in a Teat Cup.
2004 NMC Annual Meeting Proceedings, , pg. 176-188 (Mein et al).
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