SHORT-TERM SELECTION FOR BODY WEIGHT AND GROWTH RATE IN JAPANESE QUAIL 1. DIRECT SELECTION RESPONSE

Document Type : Research articles.

Authors

1 Poultry Production Dept., Faculty of Agriculture, Fayoum Univ., Egypt.

2 Animal Production Research Institute, ARC, Dokki, Egypt.

Abstract

Three quail lines were used in this work to study the effects of
mass selection for increased body weight or growth rate: HBW42 line
was selected for high body weight at 42 day of age, HGR1-42 line was
selected for high growth rate during the period from one-day to 42
day of age and randombred control line (RBC) was maintained as
non-selected pedigreed population over three generations of
selection. The following results were obtained:
There was an asymmetry in the direct response to selection in
the male and female BW and GR favoring females. After three
generations of mass selection, the HBW42 line exceeded the RBC by
8.40g (4.81%) and 13.66g (7.53%) for males and females,
respectively. The regression coefficients were higher for females
than males after the 3rd generation being 2.28g (1.295%) for females
vs 0.475 g (0.315%) for males than the RBC. After three generations
of mass selection, GR1-42 line decreased from 184.1 to 183.8% for
males and 184.9 to 184.2% for females. Females had significantly
higher response on generation number either as a deviation or as a
percent deviation from the controls. The ratios of effective to the
realized selection differentials for the selected lines and sex groups
were more than unity, except for females in the 1st generation of
selection for HGR1-42 line which was indicating that natural selection
for fitness did operate in the opposite direction of artificial selection.
The more than unity ratios in all sex groups of the HBW42 line and
males of HGR1-42 line indicated that natural selection did not affect
artificial selection. Selection yielded, with few exceptions,
consistently lower heritability estimates in the selected lines,
regardless of the estimation method. The unweighted mean of
heritability estimates either for male or female progeny weights
indicated that non-additive, primarily and maternal effects may be
affected body weights. The larger h2S for females of HGR1-42 line in
the 2nd and 3rd generations of selection than h2D indicated sex-linked
effects. Females had considerably higher realized heritabilities than
males. The realized heritabilities obtained for the HGR1-42 line were
generally higher than those for the HBW42 line (0.69 vs 0.41).
Generally, as generation number increased realized heritabilities for
the selected traits in all sex groups decreased. The rate of decline in
magnitude of heritabilities was higher in the HGR1-42 line than the
HBW42 line. Whereas, the heritabilities of all sex groups for the RBC
were higher than those for the selected lines. It can be concluded that
the direct response for HBW42 line was greater than those of the line
selected for HGR1-42 compared to their controls.

Keywords

Files

Share

How to cite

Statistics