Western blot analysis of MEF2B protein level in LM of 4 cattle breeds at 3 stages of postnatal development. (A) Representative blots of MEF2B and GAPDH protein; (B) ratio of relative protein levels of MEF2B expressed to GAPDH. GAPDH was used as a loading control, as indicated. Data are representative for three independent Western blot analyses performed using extracts from 3 bulls of each experimental group. Results are expressed as mean ± SE. Statistically significant differences (**P < 0.01; ***P < 0.001) in MEF2B protein levels were calculated within breed in a given age group. LIM, Limousine; HER, Hereford; HF, Polish Holstein-Friesian; PR, Polish Red.