Report on the Agricultural Experiment Stations, 1953 Page: 31
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LIVESTOCK PRODUCTION AFFECTED BY ANIMAL DISEASES 31
grazing and that care should be taken that calf pastures carry a minimum
parasite population or, better still, that calves be kept in dry
lots, free of vegetation.
Phenothiazine therapy in cattle
Experiments at the Louisiana station on the prevention of losses
due to parasitism in calves by low-level feeding of phenothiazine in
the grain ration, indicate the following facts in pure infections of
the large stomach worm (Haemonchus contortus). When calves are
fed phenothiazine at the rate of 11/2 grams per day, eggs usually cease
to be found in the manure within about 2 weeks. In all animals the
eggs become abnormal in about 48 hours after phenothiazine feeding
is begun and infective larvae are not recovered from the manure.
Under phenothiazine treatment future infections are prevented and
protection is afforded to the younger, more susceptible animals. Similar
experiments gave comparable results in cases of pure infections
of the nodular worm and hookworm.
When the drug is fed during the first 2 weeks of the prepatent or
larval period of the parasite within the calf, it does not cause interference
with the normal development of the larvae in these early
stages. Thus the symptoms of parasitism and the losses will not be
prevented when the larvae are already on the premises and infections
induced by the larvae are evident at the time the feeding of the
drug is begun. Previous experiments have demonstrated also that
phenothiazine offers no protection from symptoms in pure infections
of the nodular worm.
Phenothiazine given to healthy suckling calves nursing cows on an
adequate diet did not retard gains, according to a Texas station report.
Additional evidence that use of phenothiazine in feed constitutes a
more effective treatment for lungworms in cattle than any drug now
available, and that continuous low-level dosage of phenothiazine in
feed does not affect palatability, is being obtained in Oklahoma station
Parasitic damage to swine livers
Internal parasites of swine cause a heavy annual loss to the meat
industry. A study made by the Virginia station revealed that twothirds
of the livers from 33,655 hogs slaughtered over a 12-monthperiod
at three federally inspected abattoirs in southeastern Virginia
were condemned as unfit for human consumption because of parasitic
damage to them. This resulted in an estimated loss of 60.5 cents for
every hog slaughtered.
Swine ascarid eggs persist in the soil
Approximately 2 years after a l/4-acre pasture at the Michigan station
was seeded with Ascaris eggs six young pigs were run on this
pasture and then were sacrificed at 2-week intervals. All of these
pigs had extensive liver scars due to worm migration. Three littermates
held on Ascaris-free concrete floors, however, did not develop
liver lesions. This confirms results of an earlier study conducted by
the Department. Thus the popular idea that hog lots not used for
2 years are safe from this form of parasitism is subject to considerable
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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/m1/33/: accessed February 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.