cjs-200704-0001 ArticleInAPeriodical 2007 Czech Journal of Animal Science 52 4 83-87 MatějíčekA. MatějíčkováJ. NěmcováE. JandurováO.M. ŠtípkováM. BouškaJ. FrelichJ. Joint effects of CSN3 and LGB genotypes and their relation to breeding values of milk production parameters in Czech Fleckvieh The objective of this study was to estimate the joint effects of CSN3 and LGB genotypes on breeding values of milk production parameters. CSN3 (kappa-casein) and LGB (beta-lactoglobulin) genotypes of 120 Czech Fleckvieh sires were detected using the PCR-RFLP method. Breeding values of sires were obtained from the Official Database of Progeny Testing. Ten genotype combinations were detected. Genotypes ABAB (25.0%), ABAA (13.3%) and ABBB (13.3%) were the most frequent. Significant effects of genotype combinations on breeding values for fat and protein content were found. The highest breeding values for milk (+621 kg) and protein (+15.8 kg) yields were associated with genotype combination ABAA, while the highest breeding values for content parameters (+0.15% for protein content and +0.55% for fat content) were associated with genotype combination BBAB.