Fluorescence images of semitendinosus muscle transverse sections of Holstein Friesian fetuses at (a) 3, (b) 4.5, and (c) 6 mo of gestation
immunostained for slow myosin (MYH7; Acris Antibodies GmbH, Herford, Germany). The primary antibody against slow myosin was detected with an Alexa
Fluor 488 labeled rabbit anti-mouse IgG (MoBiTec, Göttingen, Germany) secondary antibody. Note the increasing fluorescence intensity of primary fibers from
3 to 6 mo of gestation. Arrows indicate secondary fibers positive for slow myosin. Scale bar: 50 μm