EN
Osteochondrosis (OC) is a developmental bone disease of serious clinical consequences that occurs in various anatomical locations. This disease is frequently seen in pigs, horses, poultry, and dogs, and has also been described in humans. Osteochondrosis, often referred to as leg weakness, is a common problem in pig herds. It causes economic losses and is considered as an animal welfare issue in pig production. Most traits related to animal health and welfare are complex, difficult to define, and often characterized by low heritability. Osteochondrosis is a multifactorial disease, and its etiopathogenesis can be traced to a combination of genetic, environmental and mechanical factors, as well as stress. Environmental factors thought to be important in the modulation of gene expression include nutrition, disease, and physical weight-bearing conditions. Feeding and management conditions (floor type, humidity, etc.) have influence on the development of osteochondrosis in pigs susceptible to this disease. The genetic background of osteochondrosis, which resembles tissue alterations related to aging and degeneration, has also been examined and identified. The heritability of leg weakness in pigs of different breeds ranges from 0.2 to 0.6. As the defect is hereditary, it should be controlled in the course of selection. It is well known that there are two approaches for genetic evaluation of complex and quantitative traits: genome-wide scanning and candidate gene approaches. Recent studies of the pig genome, presented in numerous scientific publications, point to the possibility of identifying the chromosome regions that carry the genes connected with osteochondrosis - the so-called QTL (Quantitative Trait Loci). The presence of QTL with an impact on osteochondrosis was established on chromosomes 5, 13, and 15. Other QTL studies identified eleven QTL affecting leg weakness on eight autosomal chromosomes. Some authors suggest that three QTL associated with osteochondrosis may be located on SSC2, SSC6, SSC10. Candidate genes are generally defined as those that have an important, direct or indirect, effect on the trait of interest. By focusing on candidate genes that play roles in the biology of bone and cartilage development it may be possible to understand the biological background of traits related to leg weakness. Studies of candidate genes for OC have focused on cytokines, growth factors, genes that encode components of bone matrix, and genes that encode receptors for calciotrophic hormones, yielding more than 200 potential candidates. Some of them are presented in this paper. In recent years, genomic selection based on candidate genes, as well as on SNP markers and SNP microarrays, has become a promising tool for the breeding of osteochodrosis-free pigs.