Document Type : Research articles.
Authors
Poult. Prod. Dept., Fac. Agric., Fayoum Univ., Egypt.
Abstract
Chicks of two selected lines of Japanese quail for high six weekbody weight and high 1-6 week growth rate (HBW6 and HGR0-6) over
three generations were used to partition the variability of growth and
carcass traits. A randombred control line (RC) was kept in order to
facilitate comparison between lines. The RC had the lowest boneless
meat% (BLM), fat% and live body weight at slaughter (LBW6) being
48.13%, 16.09% and 184.65g, respectively. Although HGR had the
highest BLM% and dressing%, birds of this line had significantly
poorer feed conversion (FC) and performance index (PI) than other
lines. On the other hand, birds of the HBW line had the highest LBW6
and PI but had higher carcass' fat% (200.25g, 3.55 and 20.51%,
respectively). Sex significantly affected BLM%, carcass %, dressing%,
LBW6, FC and PI. Although males had significantly higher carcass%,
their PI were poorer than females, this may be due to the superiority of
females growth than males at different ages of growth and this
difference may be attributed primarily to the relatively large ovaries,
liver and intestines of the females. When these parts were excluded,
lower carcass% for female was obtained. Except triglycerides (TG),
line significantly affected all plasma constituents. The RC line had the
highest growth hormone (GH) and the lowest albumin (Alb), total
lipids (TL), total protein (TP), triiodothyronine (T3) and ratio of T3 to
thyroxine (T3/T4). Whereas, HGR had the lowest GH and the highest
Alb, TP, T3 and T4. Females had significantly higher Alb, TP and T3/T4
than males, however, males had higher T3 than females. The results of
path analyses revealed that the studied plasma constituents measured at
three weeks of age in both sexes could be used to predict carcass traits
and growth productive performance in Japanese quail. Each of GH,
TG, TL, Alb, TP and T3/T4 was the first contributors of studied
productive traits in line by sex groups indicating direct effects which
ranged from 0.530 to 0.763, 0.504 to 0.945, 0.887 to 0.906, 0.513 to
0.990 and 0.609 to 0.892, respectively. Plasma constituents showed
higher indirect coefficients of determination for their effects on all
studied productive traits than their direct effects. This suggests that a
part of the variations in these traits could be attributed to a trait or
more, not handled in this study and may diminish the random error
variation when considered.
Keywords
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