The experiment investigated supplementation of maternal metabolizable protein in an isocaloric diet during late gestation on fetal organ growth and skeletal muscle development in sheep. Although fetal body weight was unaffected by treatment, visceral organ weights were sensitive to MP treatment as alterations in small intestinal mass and perirenal adipose tissue content suggest impacts on postnatal growth. Two-dimensional gel electrophoresis and mass spectrometry compared the sarcoplasmic and myofibrillar protein fractions of fetal skeletal longissimus muscle, identifying spots from the sarcoplasmic and myofibrillar protein fractions (30 and 12, respectively). Increased expression of fructose-bisphosphate aldolase in fetal muscle from protein-supplemented and protein-restricted ewes when compared to those from control ewes suggests a positive influence on rate of glycolysis and muscle turnover in these offspring. Further research on maternal supplementation with metabolizable protein in isocaloric diets is needed to improve fetal growth efficiency, thereby optimizing offspring performance.