Genetic analysis of partial egg production records in Japanese quail using random regression models

Laying performance, genetic parameters, and the expression of FSHβ, LHβ, FSHR, and LHR genes in Japanese quails selected for early egg production

Investigating the impact of early egg production selection (the first 90 d of laying) on egg production features, cumulative selection response (CSR), and the mRNA expression of gonadotropins (FSHβ and LHβ), and their receptors (FSHR and LHR), in Japanese quails was the goal. The selection experiment involved 1293 females in all, 257 from the base group and 1036 from the 4 selected generations. Age and body weight at sexual maturity (ASM, BWSM), weight of the first egg (WFE), days to the first 10 eggs (DF10E), egg mass for the first 10 eggs (EMF10E), egg weight (EW), egg number at the first 90 d of laying (EN90D), and egg mass at the first 90 d of laying (EM90D) were all recorded. Most egg production traits had heritability estimates that were low to moderate and ranged from 0.17 to 0.33., where the highest estimates were reported for EN90D (0.33) and BWSM (0.32). With the exception of EN90D, low to moderate positive genetic correlations were observed between ASM and other egg production traits (0.17-0.44). The fourth generation showed significantly (P < 0.05) lower ASM and DF10E but higher BWSM, WFE, EN90D, EM10E, and EM90D when compared with the base generation. CSR were significant (P < 0.05) for ASM (-6.67 d), BWSM (27.13 g), WFE (0.93 g), DF10E (-1.25 d), EN90D (7.24 egg), EM10E (10.57 g), and EM90D (140.0 g). FSHβ, LHβ, FSHR, and LHR gene mRNA expression was considerably (P < 0.05) greater in the fourth generation compared to the base generation. In conclusion, selection programs depending on the efficiency of egg production (EN90D) could improve the genetic gain of egg production traits and upregulate the mRNA expression of FSHβ, LHβ, FSHR, and LHR genes in selected quails (fourth generation). These findings might help to enhance breeding plans and create commercial lines of high egg production Japanese quails.

Influence of Improved Microclimate Conditions on Growth and Physiological Performance of Two Japanese Quail Lines

Microclimate parameters (ammonia, ambient temperature, heat index, and relative humidity) surrounding birds affect the production and health status of poultry. Therefore, this study aimed to evaluate the impact of adding natural zeolite to the litter of Japanese quail on improving microclimate parameters and its reflection in growth performance, blood gases, and blood biochemical parameters. A total of 1152 chicks were obtained from the same hatch at the 20th selection generation. Chicks were allocated into two groups based on the litter composition: Group 1: wheat straw as litter (untreated group); Group 2: 80% wheat straw + 20% zeolite (treated group). Each group consisted of 576 chicks: 410 selected line chicks and 166 control line chicks. Significant and favorable effects of the treatment on microclimate parameters during tested periods were found to favor the treated group. Either the treated group or the selected line had significantly better growth performance than the untreated group and control line. Zeolite-treated quails had significantly desirable blood gases and lower blood acidity and serum total iron binding capacity compared to the untreated group. Thus, adding natural zeolite to the litter enhanced the microclimate parameters that improved growth performance, blood gases, and blood biochemical parameters and reduced ammonia emission.

Genetic parameters of weekly egg production using random regression models in two strains of Japanese quails

The main objective of the present study was to detect the most appropriate random regression model for estimating the genetic parameters of weekly egg production. Two strains of Japanese quails including wild and white quails and pure and cross mating methods were considered. The egg collection started at the seventh week of age and lasted for 7 weeks. A random regression model using Legendre polynomial was used to analyze the weekly egg records. The model with Legendre polynomial of order 1 for the additive genetic and order 3 for permanent environmental effect was chosen as the appropriate model, based on Bayesian information criterion (BIC) and Akaike information criterion (AIC). The heritability estimates for weekly egg production were low (ranging from 0.06 to 0.09). Furthermore, the ratios of permanent environmental variance to the phenotypic variance were almost moderate, varying from 0.18 to 0.44. Genetic and phenotypic correlations between weekly egg records ranged from 0.65 to 0.93 and from 0.27 to 0.67, respectively. These results indicated that the selection based on the early egg numbers could effectively improve egg production in later periods. Furthermore, the efficiency of egg production can be enhanced with a combination of breeding programs and management strategies.

Genetic evaluation of growth in Barki sheep using random regression models

The objective of the current study was to estimate covariance components of growth at different ages from birth to yearling in Barki lambs. A total of 16,496 records for body weights at birth (W0), 3 (W3), 6 (W6), 9 (W9), and 12 (12) months of age for Barki lambs were available. Two statistical approaches were used; multi-trait (MT) and random regression (RR) animal models assuming two random effects only, additive genetic effect (σ²_a) and permanent environmental effect (σ²_pe) of the animal. Regarding the RR model, Legendre polynomials (LP) of different orders for the random parts were compared in order to evaluate the most appropriate model. Bayesian information and Akaike information criteria suggested that the optimal RR model included the third order for fixed effect of lamb age and σ²_pe, and fourth order of LP for σ²_a (LP₃₄₃). Estimates of direct heritability (h²_a) from LP₃₄₃ showed an ascending pattern, as it was 0.06 ± 0.03 for birth weight and reached to the peak at 9 months (0.42 ± 0.02). Thereafter, it declined again at the end of trajectory (12 months of age; 0.27 ± 0.03). The MT model showed a fluctuated pattern and lower estimates of h²_a (0.19 ± 0.03, 0.11 ± 0.02, 0.12 ± 0.02, 0.11 ± 0.03, and 0.16 ± 0.04 for W0, W3, W6, W9, and W12, respectively). Considerably, similar ascending patterns of the ratio of σ²_pe to phenotypic variance were reported from both RR (from 3 to 50%) and MT models (from 5 to 20%). Of interest, the RR model showed higher predicting ability of the breeding values compared with the MT model, which is an indicator for the suitability of RR models for analyzing the consecutive growth traits in sheep. Results suggested that the Barki sheep has a potential for genetic selection based on weight at different ages with selection likely to be more efficient at 9 months of age.