Identification of different allelic forms of myostatin gene and investigation of body weight and carcass biometric traits measured by ultrasound in Kurdi sheep

Myostatin gene is an inhibitor of skeletal muscle developmentmutations in its coding regionpromotesmuscle growth in some breeds, mutation of the myostatin gene has a significant effect on the increase of the body weight and carcass traits. This study was aimed to investigate the polymorphisms in exon 3 of the myostatin gene and evaluate investigation of body weights and carcass traits measured by ultrasound in Kurdi sheep.

In this study, back fat thickness and loin muscel area traits were measured by ultrasound instrument. Blood samples were collected randomly from 139 Kurdi sheep and following DNA extraction, a 388 bp fragment from exon 3 of myostatin gene was amplified. For genotyping of myostatin gene, PCR-SSCP, PCR-RFLP, and direct sequencing techniques were used. To determine the fixed effects of gender, birth type and birth year on the studied traits, GLM procdure of SAS software was used. Least square means comparison of different fixed effects subclasses was carried out by Tukey-Kramer test at 5% probability level. To measure the relationships between tarits, pearson correlation was used.

In PCR-RFLP technique, after enzymatic digestion of all samples, only one genotype was observed and this locus was monomorphic. PCR-SSCP analysis showed two band patterns A and B, which were very similar in shape. Therefore, to determine the actual genotype, some samples with different band patterns were evaluated by direct sequencing technique. The results showed that there is no polymorphism among samples. The mean ultrasonic fat thickness and loin muscle area in this study were 0.46 cm and 7.78 cm2, respectively, with an average body weight of 43.42 kg at the time of ultrasonography. The correlation between the two ultrasound carcass traits (UBF and UMA) was positive (r=0.84, P<0.0001). The lowest correlation coefficient of carcass fat thickness and ocular muscle area with the studied traits were 0.02 and 0.3, for birth weight and weaning traits, respectively. The highest correlation coefficient of the studied traits with carcass fat thickness and loin muscle area were 0.82 and 0.87 for body weight at the time of ultrasonography and middle tail width, respectively (P=0.001).

In this study, using PCR-SSCP, PCR-RFLP and direct sequencing, only one genotype was detected in the myostatin gene. Considering that various studies have introduced the mutated allele of the myostatin gene as an effective allele on the double muscling for breeding and improving the quality and quantity of meat, the studied herd did not have the allele. Considering the relatively suitable diversity observed in the studied traits, especially the carcass traits measured by ultrasound, there will be a possiblity to improve the traits through selection.