Author:
WOOLFORD MURRAY W.,WILLIAMSON JOHN H.,HENDERSON HAROLD V.
Abstract
Cows with subclinical intramammary infections were identified by
milk
bacteriology. The mastitis pathogens included Staphylococcus aureus
(n=9), Streptococcus uberis (n=10) and
coagulase-negative staphylococci (n=10). Samples
of first fore milk, main flow milk and strippings milk fractions were collected
from
each quarter and laboratory measurements were made of electrical conductivity,
milk fat concentration and somatic cell count. Conductivity measurements
were
corrected for milk fat concentration and within-cow inter-quarter conductivity
ratios calculated. Repeatability estimates of all measurements between
days were
calculated. In the case of infected quarters, all conductivity values decreased
markedly (P<0·05) from first fore milk to
main flow milk fractions. Conductivity
differences between quarters of infected cows were substantially lower
during the
main milk flow phase. For quarters infected with Staph. aureus
an increase in
conductivity was observed (P<0·05) from
main flow to strippings fractions. For
uninfected quarters, conductivity declined as milk fat concentration increased
with
successive milk fractions. Variation, both within and between milk fractions,
was
greater for somatic cell count than for conductivity. Differences in conductivity
between milk fractions from individual infected quarters were not accounted
for by
changes in fat concentration and may result from the mixing of milk from
infected
and uninfected regions of the gland. Localized infection may produce a
decrease in
conductivity between fore milk and mid-flow fractions while differential
drainage
from an infection site in the secretory tissue may additionally produce
an increase in
conductivity from mid-flow to strippings fractions. Such changes may thus
provide
information on the location and magnitude of an infection. The results
clearly
demonstrate the importance of the milk fraction when using conductivity
as a
diagnostic of intramammary infection, the highest diagnostic sensitivity
being
achieved by using first fore milk samples.
Publisher
Cambridge University Press (CUP)
Subject
Animal Science and Zoology,General Medicine,Food Science
Cited by
49 articles.
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