Report on the Agricultural Experiment Stations, 1953 Page: 34
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34 REPORT ON EXPERIMENT STATIONS, 19 5 3
losses from blackhead in chickens. However, this did not prove to
be the case. Feeding Enheptin to 12-week-old White Leghorn cockerels
at therapeutic levels of 0.1 percent for 2 weeks, and at 0.05-percent
level during the third week at the New Jersey station resulted in a
complete inhibition of sexual maturation in these birds. Feeding
cockerels Enheptin caused a reduction in the size of comb and a
shriveled comb structure, a reduction in the size and activity of the
testis, infertility, and generally complete sexual regression. In later
research, a daily average drug intake of 41.0 milligrams was found
to be sufficient to cause complete suppression of sexual development
of both pullets and cockerels. When treatment was discontinued,
both males and females required approximately 10 weeks to recover
from the drug effects.
Preliminary experiments at the Michigan station have indicated that
chick or turkey embryos are not suitable environments for the growth
of the blackhead organism. This contributes further evidence against
the hypothesis of certain workers that the organism can be transmitted
by the avian egg.
In continuing its experimental work with bacteria-free suspensions
of Histomonas meleagridis, the Maryland station has shown that the
parasite is not dependent on associated bacteria for its pathogenic
Large roundworms of fowls
Little is known of the effect of some parasites on their hosts.
Experiments have been conducted by the Michigan station on the
effect of Ascaridia galli infections on the thymus gland in chicks in the
presence and absence of vitamin B12. The results clearly indicate
that these roundworm infections induce a thymic atrophy in the
bird either in the presence or absence of vitamin B12. Although this
atrophic condition results from the vitamin deficiency alone, it is more
pronouced when the birds are infected with the parasite.
Experiments were conducted at the Kansas station to determine
effects of aureomycin and/or vitamin B12 (at levels used in commercial
feeds) on the resistance of chickens to Ascaridia galli, the large roundworm
of fowls. Aureomycin or vitamin B12, or a combination of both,
reduced the incidence of infection and lowered the mortality rates
resulting from ascariasis among the experimentally infected chickens.
The addition of aureomycin and vitamin B12 to an all-plant protein
basal diet significantly stimulated the growth of the chickens, whether
they were parasitized or not. Of particular importance, however,
is the fact that there were no significant differences in the weight
gains made by parasitized versus nonparasitized .chickens fed only
the basal ration, whereas parasitized chickens fed the supplemented
ration made significantly inferior weight gains as compared with
weight gains of the nonparasitized chickens fed the supplemented
ration. The increased growth rate of the nonparasitized chickens
fed the fortified diet places increased importance on ascariasis. Some
evidence was shown that ascariasis likewise decreased the feed efficiency
of the fortified feed. Accordingly, if poultrymen and farmers
are to obtain maximum growth responses from feeds fortified with
these supplements, they must continue to use known control measures
against the large roundworm.
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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/m1/36/: accessed July 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.