Both leg and crown-rump lengths are measurements
of bone growth, which is linear in cattle fetus. Different
patterns between leg length and leg weight development
implied that fetal weight and size are not coordinated during
the gestation. A linear increase in fetal size suggests that the
skeletal system and associated frame score of the animal is
established early with development of bone.
Breed differences were noted for most body traits as
early as 3 mo of gestation, yet more robustly at 9 mo
(Tables 2 and 3). Galloway had the least BW, half carcass
and leg weights and the significant shortest leg length at all
gestational ages. At 3 mo, fetuses from Holstein Friesian
had a significantly greater BW, half-carcass weight, leg
weight, and leg length compared with German Angus and
Galloway, respectively. Belgian Blue fetuses had
significantly greater BW at 9 mo of gestation compared
with German Angus and Galloway, respectively, but no
significant difference was observed between Holstein
Friesian and Belgian Blue. Before 6 mo of gestation, there
were no significant differences in half-carcass weight and
leg weight between Holstein Friesian and Belgian Blue, but
fetuses from Belgian Blue had the significantly greatest
half-carcass weight and leg weight among all investigated
breeds at 9 mo of gestation. This result suggests that muscle
tissue grew more rapidly in Belgian Blue than in the other
breeds after 6 mo of gestation.
Our results support the findings of Reynolds et al.
(1990), who reported that calves from large framed sire
breeds had heavier BW at 6.5 mo of gestation and at birth
than calves from medium-sized sire breeds. Also Ferrel
(1991) showed that fetal weight of Brahman cattle at 7.7 mo
was significantly smaller than Charolais. In contrast, Gore
et al. (1994) reported that the BW of Angus and Chianina
were not significantly different at 3.3 and 6.7 mo of
gestation, and 1 mo after birth. In our study, cattle breeds
with different postnatal growth impetus and muscularity
had significant differences in body traits as early as 3 mo of
gestation, and these differences were maintained at birth