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Abstract
Body compositions of a randombred control population (RBC2), a line selected for increased
16-wk BW (F), a line selected for increased shank diameter (FL), and a line selected
for increased leg muscle mass (FM) were compared at 16 wk of age. The F line originated
from the RBC2 population and the FL and FM lines were developed as sublines of the
F line. The F and FL lines were developed through mass selection of BW and shank width,
respectively. The FM line was developed through family selection for leg muscle mass.
Selection for BW in the F line has resulted in an increase in the proportion of breast
muscle and a decrease in the relative amount of leg bone in comparison with the RBC2
population. Selection for increased shank width in the FL line has increased not only
shank weight but has produced concomitant increases in the weight of the tibiotarsal
and femur bones. Although FL line has also shown a correlated increase in BW in association
with increases in shank width the increase in leg bone weight was relatively greater
than the increase in BW. Therefore, the relative weights of leg bones in the FL line
increased such that they were more similar to the RBC2 population than to the F line.
Although the amount of leg muscle increased slightly in the FM line, the relative
proportion of leg muscle did not increase significantly. The selection program used
was probably ineffective in increasing the proportion of leg muscle because of the
high percentage (low selection intensity) of families selected and small family size
for estimating family means.(ABSTRACT TRUNCATED AT 250 WORDS)