Simple SummaryThe objective of this study was to evaluate the effect of differentmyostatinalleles on muscularity of four body parts and overall muscularity, and, moreover, on calving ease, birth weight and 205-day weaning weight of weaned calves in the Hungarian Charolais population. Fivemyostatinalleles of 2046 calves were involved in the study. Among themyostatinalleles, the effect ofQ204Xwas statistically proved (p< 0.01 andp< 0.05) on the 205-day weaning weight, muscle score of back, muscle score of thigh, loin thickness score and overall muscle development percentage. It would be advisable to pay more attention to this allele in the breeding program.AbstractThe slaughter value of live cattle can be assessed during visual conformation scoring, as well as by examining different molecular genetic information, e.g., themyostatingene, which can be responsible for muscle development. In this study, theF94L,Q204X,nt267,nt324andnt414alleles of themyostatingene (MSTN) were examined in relation to birth weight (BIW), calving ease (CAE), 205-day weaning weight (CWW), muscle score of shoulder (MSS), muscle score of back (MSB), muscle score of thigh (MST), roundness score of thigh (RST), loin thickness score (LTS), and overall muscle development percentage (OMP) of Charolais weaned calves in Hungary. Multi-trait analysis of variance (GLM) and weighted linear regression analysis were used to process the data. Calves carrying theQ204Xallele in the heterozygous form achieved approximately 0.14 points higher MSB, MST and LTS, and 1.2% higher OMP, and gained 8.56 kg more CWW than their counterparts not carrying the allele (p< 0.05). As for theF94Lallele, there was a difference of 4.08 kg in CWW of the heterozygous animals, but this difference could not be proved statistically. The other alleles had no significant effect on the evaluated traits.