Epigenetics is defined as the study of changes in gene function that are mitotically or meiotically heritable and do not lead to a change in DNA sequence. Epigenetic modifications are important mechanisms that fine tune the expression of genes in response to extracellular signals and environmental changes. In vertebrates, crucial epigenetic reprogramming events occur during early embryogenesis and germ cell development. Chicken embryo, which develops external to the mother's body, can be easily manipulated in vivo and in vitro, and hence, it is an excellent model for performing epigenetic studies. Environmental factors such as temperature can affect the development of an embryo into the phenotype of an adult. A better understanding of the environmental impact on embryo development can be achieved by analyzing the direct effects of epigenetic modifications as well as their molecular background and their intergenerational and transgenerational inheritance. In this overview, the current possibility of epigenetic changes during chicken embryonic development and their effects on long-term postembryonic development are discussed.

The aim of this research was to study the factors affecting hatchability, percentage of egg weight loss during incubation, early embryonic mortality,

Myostatin acts as a negative regulator of muscle growth; therefore, its role is important with regard to animal growth and meat production. This study was undertaken with the objective to detect polymorphisms in the first intron and c.*1232 position of the MSTN gene and to analyze effects of the detected alleles/genotypes on growth and carcass traits in Colored Polish Merino sheep. In total, 23 traits were analyzed, i.e., seven describing lamb growth and 16 carcass traits. Single nucleotide polymorphisms (SNPs) in the first intron and the c.*1232 position were identified using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and PCR-restriction fragment length polymorphism (PCR-RFLP) methods, respectively. The MIXED procedure of the SAS software package was used to analyze allelic and genotypic effects of the MSTN gene on growth and carcass traits. Polymorphisms were only detected in the first intron of the MSTN gene. All investigated sheep were monomorphic G in the c.*1232 position. The MSTN genotype was found to have significant effect on body weight at 2nd day of life (BW2) and loin and fore shank weights. Significant allelic effects were detected with respect to BW2, scrag, leg, fore, and hind shank weights. These results suggest that polymorphisms in the first intron of the MSTN gene are relevant with respect to several carcass traits and BW2 in Colored Polish Merino sheep.

This study aimed to genotype the polymorphism (c.654G > A) in the exon 3 of the insulin-like growth factor 1 receptor gene (IGF1R) and to analyze its association with growth, body size, slaughter and meat quality traits in Colored Polish Merino sheep. In total, 67 traits were analyzed. The IGF1R polymorphism was genotyped using the polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) method. The MIXED procedure of the SAS software was used to assess the genotypic effects of the polymorphism (c.654G > A) on production traits of interest. The IGF1R c.654G > A genotypes were found to have a significant effect on the average daily gain between the 56th and 78th day of life, cold carcass, leg part, leg cut, fore shank, and kidney weights, as well as eye of loin depth, intramuscular fat content, and water-holding capacity of meat. The results suggest that the studied polymorphism may provide useful information for marker-assisted selection for increased meat performance in Colored Polish Merino sheep.

Insulin-like growth factor I, encoded by the IGF-I gene, plays a role in cell growth and differentiation, embryogenesis, metabolism regulation, skeletal growth, and protein synthesis. The aims of this study were to investigate the polymorphism in the 5′ flanking region of the IGF-I gene and evaluate associations between the single-nucleotide polymorphism (SNP) in this gene and growth, body size, carcass and meat quality traits in Coloured Polish Merino sheep. In total 78 live and post mortem traits were investigated. Polymorphism in the IGF-I gene was identified with the use of the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method in 305 Coloured Polish Merino sheep. In association studies, traits of interest were analysed with the use of the MIXED and GENMOD procedures of the SAS statistical package. Two alleles named A and B, and two IGF-I genotypes – AA and AB – were detected. The A allele and the AA genotype were predominant, with the frequencies of 91.6 and 83.3 %, respectively. The IGF-I genotype was found to have a highly significant effect on fore shank weight (P = 0.006), kidney fat class (P = 0.002) and EUROP fat class (P = 0.005). Furthermore, the IGF-I genotype significantly affected external fatness of carcass class (P = 0.038), drip loss (P = 0.049), and subjective assessment of meat colour (P = 0.043), and it tended to be associated with longissimus dorsi (LD) muscle width (P = 0.063) and flavour (0.067). Concluding, the IGF-I gene could be considered as a candidate gene of selected carcass and meat quality traits in sheep.