Abstract. The coat colour of animals is an extremely important trait that affects their behaviour and is decisive for survival in the natural environment. In farm animal breeding, as a result of the selection of a certain coat colour type, animals are characterized by a much greater variety of coat types. This makes them an appropriate model in research in this field. A very important aspect of the coat colour types of farm animals is distinguishing between breeds and varieties based on this trait. Furthermore, for the sheep breeds which are kept for skins and wool, coat/skin colour is an important economic trait. Until now the study of coat colour inheritance in sheep proved the dominance of white colour over pigmented/black coat or skin and of black over brown.

Simple Summary: Identification of mutations in the myostatin gene, affecting the occurrence of the double muscling phenotype in some breeds of beef cattle, was an impetus for further analysis and identification of mutations within this gene in other animal breeds, characterized by increased meat performance parameters. The number of geese in poultry livestock production in Poland is small. The native geese breeds can be successfully used to produce high-quality poultry meat and can be a very good source of goose meat production for regional and organic products. The aim of the study was to identify a mutation in the MSTN (Myostatin) gene and investigate whether this polymorphism can affect body weight in different periods of life in Landes and Kielecka breeds. Measurements of the examined trait were taken with time intervals to demonstrate the putative effect of the identified SNP (Single Nucleotide Polymorphism) on body weight over the course of bird growth. In conclusion, the identified c.1231C>T polymorphism suggests a possible link between the polymorphism and the BW (body weight) of Kielecka geese in the 12th week of life. The most significant factors affecting the BW values in geese are breed and sex.Abstract: Myostatin, also known as growth differentiation factor 8 (GDF8), belongs to the TGF-β superfamily of proteins. MSTN is a highly conserved protein that acts as a negative regulator of skeletal muscle growth. Loss of myostatin functionality causes the phenotype to appear in the form of 'double musculature', among others in cattle, sheep, and house mice. The presented results of the research were carried out on two geese breeds-Landes and Kielecka. The aim of the study was to identify mutations in the MSTN gene and study their impact on body weight in both geese breeds in different periods of life. Analysis of the obtained results showed the existence of polymorphism in exon 3 (c.1231C>T) and suggested a possible association (p < 0.05) between BW and genotype in 12 weeks of life in male Kielecka geese breed. The identified polymorphism may be one of the factors important for improving body weight in the studied Kielecka breed, therefore, it is necessary to conduct further research on a larger population of geese breeds in order to more accurately estimate the effect of the identified SNP c.1231C>T on BW in geese.

This preliminary study aimed to differentiate domestic pigs from wild boars based on MC1R and NR6A1 polymorphisms and to identify admixture between these genomes. We studied samples obtained from wild boars from two regions of Poland and five pig breeds: Polish Landrace, Polish Large White, Złotnicka White, Pulawska and Duroc. Along the MC1R gene sequence, we identified four polymorphic loci comprising three codons. The “wild type” allele was primarily found in wild boar but also in the Duroc and Złotnicka White breeds. Non-wild type alleles were identified in the vast majority of domestic pig samples and in two wild boar samples. Based on MC1R profiles, we conducted a population study, and revealed admixture between both genomes using STRUCTURE and NETWORK Software. Interestingly, an allelic discrimination assay with NR6A1 g.748C > T TaqMan probes revealed a clear separation of samples into two groups: wild boar samples representing the C allele and domestic breeds representing the T allele. Based on the obtained results, we conclude that NR6A1 g.748C > T is an effective marker for differentiating between wild boars and domestic pigs, where this is supported by MC1R data, to identify admixed profiles. We recommend that a larger sample of genomes is studied to verify this method.

the aim of the study was to analyse the association of ACACA and SCD1 polymorphism with milk composition, fatty acid profile in milk fat and milking performance of Polish Holstein-Friesian cows. The animals were divided according to criteria: lactation -1st, 2nd, 3rd, 4th; ACACA polymorphism -CC, CG, GG; SCD1 polymorphism -AA, VA, VV. The presence of A293V polymorphism of SCD1 gene in the population of Polish Holstein-Friesian cattle has been confirmed. In the analysed fragment of ACACA gene presence of a novel SNP has been revealed. The SNP AJ312201.1g.1488C>G consists of a substitution G>C in 1488 position. This ACACA polymorphism influenced C13:0, C14:1, C16:1 and CLA, while the analysed SCD1 polymorphism influenced C14:1. Interestingly, C16:0, C18:0 and C14:1 were influenced by fat content; while C16:1 was influenced by lactation stage; and CLA was influenced by both lactation stage and fat content. Although the novel SNP on ACACA gene and A293V on SCD1 showed only slight influence on fatty acid profile in this study, these genes are still potential candidate genes for fat content and composition in milk, but require further research.

Reproductive traits (especially litter size) are usually characterized by low heritability, and thus, phenotypic selection is often ineffective and slow. In order to improve fertility characteristics such as ovulation rate and litter size, it seems more effective to select breeding animals based on their genotype. The aim of the study was to use genome-wide association study (GWAS) in three sheep breeds to identify the genetic variants affecting the litter size in sheep. The study allowed us to identify one genome-wide significant SNP (rs402032081—located in ephrin type-A receptor 6, EPHA6) showing an association with litter size in Polish Mountain Sheep. We suggest that the EPHA6 gene can be a candidate gene for prolificacy trait in selected breeds of sheep; however, it needs further functional data for validation.