Report on the Agricultural Experiment Stations, 1953 Page: 12
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12 REPORT ON EXPERIMENT STATIONS, 1953
solution more difficult. As one organism is studied and methods for its
treatment or control are made available, another organism equally
bad arises to take its place. At first Streptococcus agalactiae was
thought to be the causative organism, but a number of other organisms
have now been shown to be involved.
Particular attention has been given by the New Hampshire station
to the diagnosis and control of staphylococci, reported by a number
of the stations as an important cause of both acute and chronic
mastitis. In some herds staphylococci produce a greater incidence of
infection than Streptococcus agalactiae and often become of special
concern in herds in which streptococcal mastitis has been eliminated.
This is in agreement with research results at the California station
where it was also found that there is a relationship between mammary
infection by staphylococci and the increase in age of the animal. The
Virginia station points out that the characteristics of these staphylococci
are similar to those found in human infections and food-poisoning,
indicating the potential danger of the organisms from that
standpoint. In one of the New Hampshire herds under study for 5
years, about 20 percent of the clean negative udder quarters became infected
with staphylococci during each year. Detailed studies were
made at that station on the characteristics of the organism and methods
for its diagnosis were developed. The station found that staphylococci
which cause either acute or chronic mastitis produce both alpha and
beta toxins. It was demonstrated that the alpha-type toxin is particularly
irritating to the mammary tissue and will produce typical
cases of acute mastitis when injected into the udder via the teat canal.
Many findings are reported by the stations on experiments with
drugs and antibiotics for control of mastitis. Of special interest is
that reported by the Michigan station. Scientists there conducted
research on radioactive penicillin infused into the normal udder of a
cow. This has shown the pattern of distribution and whereabouts
of the antibiotic under normal conditions. The results are being compared
with those of a similar study conducted on an affected udder.
The Ohio station observed that resistance of milk samples to the
action of Streptococcus agalactiae offers a possible means for estimating
the relative resistance of cows to udder infection. The method
utilized in Ohio's recent studies is based on the determination of the
acid produced by the organisms when inoculated into milk samples.
A marked loss in resistance is shown by milk samples from cows at
the beginning of the grazing season. This suggests a possible explanation
for some of the extensive herd problems at times encountered
during the early part of the pasture season. Present and previous
studies also indicate that the feeding of better quality roughages
increases milk production and tends to support resistance levels, except
when marked changes in roughage are made.
Open sheds reduce calf death losses
Although disease organisms are the primary causes of calf diseases
and mortality, a number of predisposing factors are sources of infection.
One of these is improper housing. The Missouri station reports
that calves raised in open-type structures suffered a 3.7 percent
lower death rate from the scours-pneumonia complex than calves
raised in closed buildings. Washington station calves raised in both
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1953, book, 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5989/m1/14/: accessed January 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.