|Abstract or Summary
- Three inbred and relatively unrelated lines of Hereford cattle
(1. Lionheart, 2. Prince, and 3. David) developed at the Corvallis
branch of the Oregon Agricultural Experiment Station as part of the
W-1 project of the Western States were crossed annually from 1963
through 1965 inclusive. Data on 137 inbred and linecross calves
born during the three-year period were analysed for four production
traits: birth weights, suckling rates of gain, average daily gains and
feed efficiency (pounds of feed per 100 pounds of gain). There were 79
male and 58 female calves. Twenty-three of the male calves were
inbred while 56 were linecross calves. There were 16 inbred and
42 linecross female calves.
The purpose of the study was to compare the mean performance
of any two inbred lines used to make crosses with the mean performance of their reciprocal linecrosses for possible heterotic effects.
All possible diallelic crosses were made among the three lines in each year and all calves were weaned and feed-tested on a constant-weight
basis. Male calves were feed-tested from 450 to 800 pounds
and again between 800 and 1000 pounds while female calves were
feed-tested from 400 to 750 pounds. They were fed all they could eat
for three hours each morning and three hours each evening. The
ration and other management details are described. Selection was
on an index basis with automatic culling for inherited defects and
Results were reported separately for bull and heifer calves.
Comparisons were mostly on a within-sex basis and always on a
For both male and female calves, there was no significant difference between the mean birth weights and mean suckling rates of
gain of inbred calves and their reciprocal linecross relatives. There
was a non-significant difference between male, and female inbred and
linecross calves. There was more variability among female than
among male calves in suckling gains.
On the average, linecross calves of both sexes at younger ages
within lines gained more rapidly and were more efficient than inbred
calves, with the exception of the 2 x 3 + 3 x 2 linecross male calves
which gained slightly less than their inbred relatives between 450 and
800 pounds body weight. The 1 x 2 + 2 x 1 linecross heifers were
significantly superior (P < 0.01) by 0.28 pounds per day and showed
a saving of about 113 pounds of feed per 100 pounds of gain over their inbred relatives. All linecross calves were non-significantly more
efficient in feed utilization than their within-line inbred relatives and
there were indications of more heterosis in female than male linecrosses.
However, in the 800 to 1000 pound feed test period in the males,
the mean daily gain and mean feed efficiency of each pair of inbred
lines exceeded those of the respective reciprocal linecrosses.
This reversal of growth rate and economy of gains between
linecross and inbred calves within the 800 to 1000 pound feed-test
period seems to indicate that inbred calves of the same chronological
age with linecross calves are physiologically younger and consequently less rapid and less efficient in rate and economy of gains at
earlier ages. The implication here is that inbreeding depresses
early production traits more than it does later-life traits.
Because of the low heterotic effects obtained in this study, the
suggestion is being made that, in future crosses of these inbred
lines, linecross calves from linecross dams be compared with inbred
calves from inbred dams since it is known that inbreeding of both
dam and calf affect the performance of the calf.