Greater growths of muscle mass in bulls from beef breeds (LIM, HER) than in the dairy breed (HF) stem from the differences in protein transformations and are associated with elevated expression of genes stimulating synthesis and inhibiting degradation of proteins (fst, sirt1) and decreased expression of genes responsible for inhibition of synthesis and intensification of protein degradation (mstn, smad2, hspa8, gsk3β). The gene discussed is MSTN; the disease is hydrops fetalis.