Report on the Agricultural Experiment Stations, 1953 Page: 50
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50 REPORT ON EXPERIMENT STATIONS, 1953
New breeds for high altitudes
One of two new breeds of chickens being developed at the Wyoming
station for use at high altitudes is of dominant white color, of medium
weight and growth rate, and lays brown eggs. It is outstanding in
ability to lay large numbers of eggs. When crossed with any other
breed, its offspring are always white in color. The other breed is of
light red color, similar to that of the New Hampshire, and has a very
rapid growth rate, and outstanding body conformation for meat production.
When these two breeds are crossed, the white crossbred offspring
lay as well as the dominant white parent, their eggs hatch
better than those of either parent breed, and they have a growth rate
better than the average of the parent breeds.
Effect of inbreeding on reproduction
As hybridization becomes more widespread in the poultry industry,
the consequences of inbreeding in poultry assume greater importance.
The Storrs ~Connecticut) station in 1923 and the Massachusetts station
in 1924 and 1934 reported investigations on the response of
poultry to inbreeding. The results proved that inbreeding has a depressing
effect, although different characters did not respond to the
same degree. The Minnesota station in 1948 first demonstrated the
effect of inbreeding in poultry on the performance of specific characters
by computing the regression of performance of various characters
on the degree of inbreeding. An increase in inbreeding resulted in a
considerable decrease in hatchability and egg production of about
equal proportion, and its effect on sexual maturity was intermediate,
but there was no significant change in body weight and egg weight.
At the same time the Iowa station reported that there was a decline in
egg production rate of 1.4 percent for each percentage increase in
Last year the Iowa station studied the effect of inbreeding on egg
production rate, using the records of 9,999 White Leghorns over a 14year
period. The birds were classified into 23 inbred and 3 "noninbred"
lines. Full-sib (sister-brother) and half-sib matings had been
generally practiced, and the inbreeding coefficients ranged from 0 to
85 percent. Differences in egg production among the inbred lines were
significant. Thus inbreeding appears to be a much stronger force than
selection in influencing egg production.
The North Carolina station made a similar study on data collected
over a 6-year period from 3,583 pullets of 482 dams and 64 sires, representing
one inbred line of White Leghorns and two inbred lines of
New Hampshires. There was very little crossing between the progeny
of different sires within lines, which resulted in a steady increase in the
average degree of inbreeding from 8 percent in 1946 to 52 percent in
1952. The results indicate that there was no significant change in performance
for egg weight and body weight at sexual maturity, with
an increase in the coefficient of inbreeding. Egg production, age at
sexual maturity, and hatchability of fertile eggs did show a significant
change as inbreeding progressed. The effect of inbreeding was to
decrease the egg production during the first 6 months, increase the
number of days to sexual maturity, and decrease the hatchability of
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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/m1/52/: accessed July 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.