Report on the Agricultural Experiment Stations, 1953 Page: 6
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6 REPORT ON EXPERIMENT STATIONS, 1953
in the hope of controlling granular vaginitis, gave disappointing
results. The severity of the disease was just as great in the medicated
animals as in the controls. So far, attempts by the West Virginia
station to isolate a virus agent in connection with this disease have
not been successful. Scientists at the Michigan station recovered an
organism from an acute case of granular vaginitis which, when injected
into susceptible virgin heifers, produces typical lesions 2 to 4
weeks later. Infertility is more likely to be encountered in animals
in acute stages of this disease, according to preliminary observations.
Management, nutrition, and inheritance as factors involved in reproductive
disorders are also being studied. The Nebraska station
observed difficulty in raising the production of its breeding herd to
the level desired because numerous high producers had to be culled.
Thirty percent of the cows in the herd were needed for replacements,
whereas only 36.4 percent of all calves born were heifers. This would
indicate that under the conditions existing in that herd only about 1
heifer calf in 15 could be sold as surplus or culled. It was also observed
that cows on an intake of 50 micrograms of carotene per kilogram
of body weight exhibited irregular and delayed estrus and had difficulty
producing normal calves after finally conceiving. In other
words, the more the time and the generations during which animals
are maintained on minimum carotene requirements were lengthened,
the greater were the difficulties experienced in securing normal growth
and reproduction. These findings have been confirmed by station
studies in Idaho, Oregon, Washington, and West Virginia.
Tennessee station scientists encountered no greater breeding difficulties
with heifers in high condition than with those that were not
fat. Even bulls showed no changes in fertility characteristics that
could be attributed to feed. The New York (Cornell) station found
that heifers which are underfed require about 5 months longer to
become sexually mature than do well-fed heifers.
Bulls kept on a low level of nutrition at the Minnesota station
produced as good quality semen as those maintained on a high level,
but volume of semen was less. Bulls underfed since calfhood (a balanced
diet but low in energy) by the Pennsylvania station did not
gain physical or sexual maturity as quickly as do well-fed bulls.
Blood constituents of the underfed bulls appeared normal, but the concentration
and motility of their spermatozoa were reduced.
The New Jersey station observed no significant differences between
cow families or between progeny of different bulls in breeding efficiency,
indicating that heredity has little influence upon overall
breeding efficiency. The New York (Cornell) station did find a
difference in the breeding efficiency of dams and daughters.
The Rhode Island station found no beneficial effect on conception
rate, hemoglobin levels, or on granular vaginitis in young heifers as
a result of adding a complete mineral mixture to the ration. This
agrees with findings at the New York (Cornell) station, which showed
that specific deficiencies of vitamins or minerals, with the possible
exception of cobalt, were generally not important factors in the sterility
problem. The Washington station continues to find that the
cows in its experiments which have been fed bonemeal, irradiated yeast
(vitamin D), or a combination of the two, breed less regularly than
those on a standard ration recommended for dairy cattle in that State.
The differences are not significant.
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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/m1/8/: accessed November 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.