This study investigated the relationship between some ultrasound measurements, live weight data, and five (F94L, nt267, nt324, nt414 and Q204X) myostatin (MSTN) variants associated with beef production in Charolais cattle. A total of 390 Charolais candidate breeding bulls were weighed at birth (BIW) as well as 205 (CWW) and 400 days (FDW) of age, and ultrasonically measured for ribeye area (REA), fat thickness at rump (FRU), fat thickness at ribeye (FRI) and marbling of the ribeye (MAR) at 400 days of age. The frequency of allele C and A were high in the studied population. The F94L had a significant effect on the FRU and FRI, whereas REA significant differed between homozygous and heterozygous animals on SNP at nt267. MAR of non-mutant animals were significantly (by 04.−05 points) lower than those heterozygous for the F94L. FRI tended to be higher (0.51–0.57 cm) for mutations together nt267 and nt414, or for F94L, nt414 and nt324, but lower (0.47–0.49 cm) for nt267 and nt414 mutations. The results indicating F94L could be use in QTL selection for improving beef quality. The polygenetic effect of different MSTN mutations, as well as the effect of MSTN deficiency, would be worth investigating in the future.

The slaughter value of live cattle can be assessed during visual conformation scoring, as well as by examining different molecular genetic information, e.g., the myostatin gene, which can be responsible for muscle development. In this study, the F94L, Q204X, nt267, nt324 and nt414 alleles of the myostatin gene (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 the Q204X allele 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 the F94L allele, 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.