Search

• Estimation of genetic parameters provides valuable insights into the growth and egg production traits of Korean native chicken pure lines. • High heritability values in growth traits, particularly in KNC line Y, indicate the potential for genetic improvement through performance testing. • Low heritability estimates in egg production traits highlight the importance of implementing effective management strategies to enhance productivity. • Positive correlations among growth traits suggest shared genes, indicating that genetic improvement in one trait can positively impact other correlated growth traits. • The moderate accuracy of estimated breeding values (EBVs) underscores their effectiveness as indicators of true breeding value, supporting future genetic improvement programs in Korean native chicken pure lines. Korean native chickens (KNC) have a rich history and are highly regarded by Korean consumers owing their distinct flavors and textures. However, their slow growth and limited egg production pose challenges compared with commercial chicken breeds. To address these limitations and enhance economically important traits, such as growth and egg production, understanding their genetic foundations is necessary. We studied five KNC lines (F, H, S, W, and Y) and assessed them for weight at 8, 10, and 12 weeks of age and the total number of eggs laid. The analysis incorporated pedigree data from 50773 chickens from Hanhyup Breeder chickens. Line F showed a mean inbreeding coefficient of 0.0017, whereas the other lines exhibited lower mean values ranging from 0.0005 to 0.0028, indicating that the inbreeding levels were within an acceptable range and considered safe from extinction. The average relatedness was 0.46–1.88 % among the studied lines. Heritability estimates for growth traits in line F were relatively high (ranging from 0.32 to 0.35), indicating a significant contribution of additive genetic variance and suggesting potential for genetic improvement through performance testing. However, the heritability of the egg production trait was low (0.07–0.16), indicating a greater role of non-genetic factors in explaining phenotypic variation. Management strategies should focus on improving these characteristics. Genetic correlations revealed strong positive associations between selected growth traits (up to 0.98), whereas all growth traits were negatively correlated with the total number of eggs laid. This suggests shared genetic influences on growth traits and highlights the potential for improving multiple correlated traits by enhancing the genetic performance of one trait. We also assessed the accuracy of estimated breeding values (EBVs), which ranged from 0.55 to 0.69 and 0.42 to 0.58 for growth traits and egg production trait, respectively. These moderately accurate estimates indicated that EBVs can effectively indicate the true breeding value of an animal. To improve accuracy, it is essential to maintain reliable phenotypic and pedigree records, as well as increase the number of animals in the flock. Therefore, this study provides insights into the genetic parameters and breeding value accuracy of growth and egg production traits in KNC, facilitating future genetic improvement programs for these economically important traits. [ABSTRACT FROM AUTHOR]

• New method for generating growth and degrowth models. • Generalization of the mathematical method proposed by Santos et al. (2019). • New unicompartimental model for fitting the Athens-Canadian Random Bred cockerels data. This paper aims to propose a new method for generating growth and degrowth models. To do so, the composition operation was added to the method proposed by Santos et al. (2019). From this new method, the model proposed by the composition of von Bertalanffy with Brody was created. The proposed model was compared to other unicompartmental models already described in the literature. The evaluated models were: Logistic, Brody, von Bertalanffy, Gompertz, Richards and the Proposed one. The following evaluators were used to define the best model.: the adjusted coefficient of determination R a j. 2 , mean squares residual (MSR), Akaike Information Criterion (AIC), Mean Absolute Deviation of the residues (MAD), Bayesian information criterion (BIC), Penalizing adaptively the Likelihood (PAL) and Predictive ability of the model (ρ). The Proposed model was the most adequate to fit to the Athens-Canadian male chickens data. Thus, this work contributed, adding the composition operation. Furthermore, the model generated by this method is effective for fitting the Athens-Canadian chicken breed data. [ABSTRACT FROM AUTHOR]

• Selection-driven chicken phenome embraces varied phenotypes including pectoral angle. • We studied PA variation across divergently selected chicken breeds. • Patterns of PA relationship with performance traits were analysed. • We propose a promising PA-based auxiliary index for using in layer selection. An appreciation of the synergy between genome and phenome of poultry breed is essential for a complete understanding of their biology. Phenotypic traits are shaped under the influence of artificial, production-oriented, selection that often acts contrary to that which would occur during natural selection. In this comparative study, we analysed the phenotypic diversity of 39 chicken breeds and populations that make up a significant part of the world gene pool. Grouping patterns of breeds found within the traditional, phenotypic models of their classification/clustering required in-depth analysis using sophisticated mathematical approaches. As a result of studying performance and conformation phenotypes, a phenomenon of previously underestimated variability in pectoral angle (PA) was revealed. Moreover, patterns of PA relationship with productive traits were analysed. We propose using PA measurement as a promising new auxiliary index for selecting hens and roosters of breeding flocks in egg production improvement programs. [ABSTRACT FROM AUTHOR]

• The influence of maternal effects on offspring phenotype was significant. • Genetic correlations between direct and maternal genetic were negative. • Estimates of heritability were low for relative growth rates. • Heritability Estimates were low to moderate for growth efficiencies and Kleiber ratios. The aim of this study was to investigate the genetic and phenotypic aspects of growth efficiency-related traits in Mazandaran native chickens. For this purpose, phenotypic and pedigree data of 21 generations were obtained from Mazandaran native chicken breeding center. Studied traits included Kleiber ratio (KR), relative growth rate (RGR) and growth efficiency (EF) at different growth phases from hatch to 8 weeks of age (1-8), hatch to 12 weeks of age (1-12), 8 weeks to 12 weeks of age (8-12), hatch to sex maturity (1-SM), 8 weeks of age to sex maturity (8-SM) and 12 weeks of age to sex maturity (12-SM). Genetic parameters and (Co) variance components were estimated by Restricted Maximum Likelihood (REML) procedure under six different univariate animal models using WOMBAT software with and without considering the maternal effects. Based on the results of the best model, determined by the Akaike Information Criterion (AIC), the estimates of direct heritability ranged from 0.05 (EF8-12) to 0.32 (EF12-SM) for growth efficiency, from 0.06 (KR8-12) to 0.37 (KR8 -SM) for Kleiber ratios and from 0.06 (RGR8-12) to 0.16 (RGR1-12) for relative growth rates. Maternal heritability ranged from 0.03 (EF8-12, EF1-8) to 0.08 (EF1-SM) for growth efficiency, from 0.006 (KR8-12) to 0.097 (KR1-SM) for Kleiber ratios and form 0.03 (RGR8-12) to 0.14 (RGR1-12) for relative growth rates. Negative genetic correlations between direct and maternal additive genetic effects were estimated for all studied traits. In conclusion, significant maternal effects indicated that these effects should be considered in genetic evaluation of traits. [ABSTRACT FROM AUTHOR]

Abstract: STAT5A/B proteins are the important modulators of growth hormone, growth hormone receptor, IGF-I, prolactin and insulin signaling pathway, which are involved in growth and reproduction. Knowledge of genetic markers in such candidate genes and their association with economical traits, probably make breeding plans more efficient through MAS programs. The aim of the current study was to investigate the possible association of two SNP in chicken STAT5B gene with breeding value of growth and reproductive traits. Total of 205 individuals from breeding station of Mazandaran Indigenous Chicken were selected randomly and they were genotyped for two SNPs of C4535156T and G4533675C using PCR-RFLP technique and HhaI and RsaI restriction enzymes respectively. To estimate breeding value of the growth and reproductive traits, phenotypic information of 18 successive generations of selection in breeding station of Mazandaran Indigenous Chicken (north of Iran) was analyzed using a univariate animal model in ASREML procedure. Finally, marker-trait association analyses were performed using estimated breeding value of the traits, as dependent variable, in GLM procedure of SAS 9.1. Two alleles and three genotypes were identified for each SNP. Significant associations between C4535156T SNP with breeding value of body weight at hatch and between G4533675C SNP with breeding value of first egg weight were found. We can conclude that two SNPs in STAT5B gene are promising markers for future use in selection to increase body weight at hatch and first egg weight. [Copyright &y& Elsevier]