Semen quality and fertilization ability of myostatin-knockout boars

There is no data currently available on the semen quality and fertility of myostatin-knockout (MSTN^-/-) boars. We showed that sexually mature adult homozygous MSTN mutant boars have an obvious "double muscling" phenotype, along with a MSTN^-/- boar head, back, abdomen, eyes, and oral cavity. Additionally, no abnormalities were found in the reproductive organs. The semen color, odor, and pH also had no abnormalities. The MSTN^-/- boars showed good sexual desire. The concentration, motility, plasma membrane integrity, deformity, acrosome integrity, and mitochondrial activity of the semen presented no significant differences from those of the control semen (Duroc). The ejaculation volume of the MSTN^-/- boars was significantly lower than that of the control (168.78 ± 6.70 and 223.11 ± 21.21 mL, respectively). The rate of cleavage and blastocyst between the MSTN^-/- and control boar semen were compared by in vitro fertilization. The results showed that in the eggs fertilized by the MSTN^-/- boar semen, the two-cell and blastocyst rates were similar to those of the control semen (69.1 ± 0.7% vs 65.2 ± 1.6% and 20.2 ± 1.2% vs 22.8 ± 1.4% for the two-cell and blastocyst rates, respectively). In this study, nine healthy offspring were successfully produced through artificial insemination using the MSTN^-/- boar semen. Thus, an MSTN^-/- boar can be used as the terminal male parent and is expected to be developed into new super lean meat varieties in the future.