Report on the Agricultural Experiment Stations, 1953 Page: 45
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DAIRY PRODUCTION 45
affect breeding efficiency. The western experiment stations are most
concerned with the minimum nutritional requirements for normal
reproduction, whereas the experiment stations in the central part of
the United States have taken up the problem of concentrating superior
germ plasm most effectively, or in other words, the problem of methods
of breeding. The following excerpts from regional reports will help
the reader to better appreciate the progress that has been made and
the problems that still face the animal breeding specialist.
The Louisiana station has found no significant relationship thus
far between heat tolerance and heritability. South Carolina is recommending
that dairymen who own grade Guernsey and Jersey cows
mate them first to Holstein bulls and then mate the progeny to Brown
Swiss bulls if they wish to increase the milk production of their herds.
Dairy outcross heifers at the Minnesota station grew 20 percent more
rapidly than inbred heifers up to 6 months of age. This does not mean
that crossing inbred strains results in above average reproductive
efficiency. In fact, the North Carolina station states, "It is evident
that the application of genetic principles has little to offer in remedying
most of the commonly encountered problems regarding normal
reproductive efficiency." The New Jersey station found a tendency
toward lower breeding efficiency in their dairy herd as the degree of
The Ohio' station has sought to learn whether there is any correlation
between thyroid activity of an animal and its ability to produce
milk. This was done by measuring the protein bound iodine (PBI)
in the blood. Significant breed differences were discovered. Among
the animals studied, the breeds ranked from high to low as follows
with regard to their PBI: Jersey, Guernsey, Brown Swiss, Ayrshire,
Holstein, and the beef breeds.
According to data obtained with the South Dakota station experimental
herd, cows which give birth to twin calves usually produce less
milk the following year than cows which give birth to only one calf.
The demand for identical twins as experimental animals is constantly
increasing because differences in nutrition and management can be
more readily measured when there are no interfering genetic differences.
Although blood typing is still considered one of the most satisfactory
methods of distinguishing fraternal twins from identical
twins, the Minnesota station has found that blood type alone is not
a conclusive diagnostic test of identical twins.
The more female calves he saves, the more cows the farmer will
eventually have and the closer he can cull his herd for low producers.
A bull calf is a potential source of superior germ plasm. Every effort
is being made to safeguard the calf during the early critical
period in its life. Last year a number of stations reported that calves
fed aureomycin made better gains than those receiving no aureomycin.
But this year the Illinois station reported that no benefit was derived
from giving antibiotics when calves were making above average gains
(2 pounds per day or more for the first 6 months). The Oklahoma
station obtained as good results from feeding aureomycin by mouth
as when it was administered subcutaneously and better results than
when it was given intramuscularly. The Louisiana station obtained
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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/m1/47/: accessed March 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.