The objective of the current study was to evaluate a multi-trait selection program based on aggregated breeding values using an animal model Best Linear Unbiased Prediction (BLUP) in Japanese quail. The estimated genetic gain was compared by both mixed model and least squares methods. Data of 1,682 female Japanese quails were collected through four consecutive generations to estimate genetic gain, depending on aggregated breeding values, for age at first egg (AFE), body weight at sexual maturity (BWSM), and days needed to produce the first ten eggs (DN10). Estimates of cumulative selection response were favorable for all the studied traits and significant for AFE (-3.03) and BWSM(10.38), but not significant for DN10(-0.15). Estimates of direct heritability were moderate for AFE (0.21) and BWSM(0.25) but low for DN10(0.08), while estimates of maternal heritability were moderate for AFE (0.19) but low for BWSM(0.04) and DN10(0.01). High (0.45 to 0.56) genetic and low (-0.01 to -0.18) phenotypic correlations were observed among the studied traits. Negative (-0.23 to -0.95) correlations between additive genetic and maternal genetic effects were observed for all traits. Genetic trends were -0.76 (P=0.031), 2.54 (P=0.037), and -0.06 (P=0.052) with calculated product-moment correlations between breeding values, estimated by BLUP and phenotypic selection methods, of 0.78 (P=0.002), 0.77 (P=0.004), and 0.61 (P=0.007) for AFE, BWSM, and DN10, respectively. Aggregated breeding value estimation based on animal model BLUP could be an effective method of constructing a selection program to achieve a favorable selection response in egg production traits in Japanese quail.

Estimation of correlated response to selection in female line of Japanese quail after a short-term selection experiment was conducted. The total number of 547 female (275 selected and 272 control) Japanese quail included in the selection experiment of selection depended on aggregate breeding values based on animal model Best Linear Unbiased Prediction. Correlated selection response estimates were favourable for all the studied traits and significant (–0.38, –9.89, –12.86, –16.64, –5.08 and –8.24) for first egg weight (FEW), age at the first 10 eggs (AGE10), age at first 30 eggs (AGE30), age at first 60 eggs (AGE60), days needed to produce the first 30 eggs (DN30) and the first 60 eggs (DN60), respectively. Estimates of heritability were moderate for egg mass for the first 10 eggs (EM10), the first 30 eggs (EM30), the first 60 eggs (EM60), AGE10 and AGE30 (0.17–0.30), but low for AGE60, DN30 and DN60 (0.01–0.10). Genetic correlations between the selection criteria traits (AFE, BWSM and DN10) and the studied egg production traits were positive and ranged from 0.25 to 0.97, 0.24 to 0.95 and 0.06 to 0.98 for AFE, BWSM and DN10, respectively, whereas phenotypic correlations ranged from 0.12 to 0.89, 0.01 to 0.34 and 0.06 to 0.87 for the same traits. The favourable genetic response obtained for egg traits could be an indicator for improving egg production performance in Japanese quail.

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This study was carried out to identify the white plumage in Japanese quail and compare it with the brown-type quail for possible genetic and phenotypic differences associated with the plumage colour, estimate the genetic and phenotypic correlation coefficients between both body weight (BW) and shank length (SL) at different ages from hatch up to 35 days of age based on weekly intervals and the age at the first egg (AFE), number of days needed to produce the first 10 eggs (DN 10 ), number of days needed to produce the first 30 eggs (DN 30 ), age at first 10 eggs (AGE 10 ), age at first 30 eggs (AGE 30 ), egg mass of the first 10 eggs (EM 10 ), egg mass of the first 30 eggs (EM 30 ), number of eggs produced in the first month (EN FM ), number of eggs produced in the second month (EN SM ), number of eggs produced in the first two months (ENF TM ), egg mass for the first month (EM FM ), egg mass for the second month (EM SM ) and egg mass of the first two months (EM FTM ) which individually recorded by bird.The main results are summarized as the following:1-The brown genotype had significantly heavier BW at the ages 21, 28, 35 day and at sexual maturity, where longer SL at 7 and 21 day of age than the white genotype. The white genotype had significantly heavier BW at one day old than the brown genotype.2-The brown genotype matured at earlier age than the white genotype (P≤0.05) by 6.08 days. However, the white genotype had longer days that needed to produce the first 30 eggs(P≤0.05) by 8.66 days and attained the first 10 and 30 eggs at later ages (27.32 and 38.34 days of age) than the brown genotype.The brown genotype showed numerically higher estimates(P≥0.05) for DN 10 , EM 10 , EM 30 , EN FM , EN FTM , EM FM , EM SM and EM FTM than the white genotype.In conclusion, the results of the present study indicated that there were significant differences between the two genotypes, brown and white in the phenotypic and genetic parameters of most studied traits favoring significantly the brown quail for growth traits except BW1 and numerically egg production-related traits (DN 10 , EM 10 , EM 30 , EN FM , EN FTM , EM FM , EM SM and EM FTM) than the white quail that could be used in breeding programs to improve these genotypes.

The main objectives of this study were to detect the most appropriate random regression model (RRM) to fit the data of monthly egg production in 2 lines (selected and control) of Japanese quail and to test the consistency of different criteria of model choice. Data from 1,200 female Japanese quails for the first 5 months of egg production from 4 consecutive generations of an egg line selected for egg production in the first month (EP1) was analyzed. Eight RRMs with different orders of Legendre polynomials were compared to determine the proper model for analysis. All criteria of model choice suggested that the adequate model included the second-order Legendre polynomials for fixed effects, and the third-order for additive genetic effects and permanent environmental effects. Predictive ability of the best model was the highest among all models (ρ = 0.987). According to the best model fitted to the data, estimates of heritability were relatively low to moderate (0.10 to 0.17) showed a descending pattern from the first to the fifth month of production. A similar pattern was observed for permanent environmental effects with greater estimates in the first (0.36) and second (0.23) months of production than heritability estimates. Genetic correlations between separate production periods were higher (0.18 to 0.93) than their phenotypic counterparts (0.15 to 0.87). The superiority of the selected line over the control was observed through significant (P < 0.05) linear contrast estimates. Significant (P < 0.05) estimates of covariate effect (age at sexual maturity) showed a decreased pattern with greater impact on egg production in earlier ages (first and second months) than later ones. A methodology based on random regression animal models can be recommended for genetic evaluation of egg production in Japanese quail.