The aim of the study was to determine the performance of four Polish breeds of goats and to evaluate the impact of αs1 -casein genetic variants on milk, fat, protein yields and casein content. The investigations included a total of 598 goats of four breeds, i.e. white improved, colour improved, white non-improved and colour non-improved. Goat productivity was established in relation to milk yield, fat and protein and the percentage of these components. Additionally, each goat’s milk was sampled to establish the fat, protein and casein content and to determine milk as1-casein genotype. As far as the αs1 -casein genotypes were concerned, the animals were assigned into two groups: strong, including variants AA, AB, AE, BE and medium . EE. It was found that the improved goats compared to the non-improved generally obtained higher scores for milk yield and, in turn, fat and protein. The concentration of the basic milk components was also highest in colour improved goats, whilst the protein/fat ratio most beneficial in white improved animals. It was ascertained that strong αs1 -casein variants tend to promote higher concentrations of the basic milk components, i.e. fat, protein and casein. In the group of animals characterized with the highest fat concentration (over 5%), protein (over 3.2%) and casein in particular (over 2.4%), animals with strong αs1 -casein genotypes clearly predominated in all four breeds of goats.
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