A study on muscular hypertrophy in cattle: serum concentrations of IGF-1, cortisol, insulin and testosterone

To gain insight into the hormonal control of muscular hypertrophy, a trial was performed with 46 young bulls, some with muscular hypertrophy (H; 12 Piemontese, HP; 10 crossbred Piemontese X Friesian, HP X F) and some without, (N; 12 Piemontese, NP; 12 Friesian, NF). The young bulls were reared under the same environmental conditions from 7 to 14 months of age. Blood samples were taken every month from the jugular vein and serum concentrations of insulin-like growth factor-1 (IGF-1), cortisol, insulin and testosterone were determined by radioimmunoassay. Data were analysed by analysis of variance, using a mixed nested and factorial model. Significant differences were found between H and N cattle for IGF-1 (270 vs. 422 ng/ml; P < 0.05) and insulin (14.3 vs. 20.7 muU/ml; P < 0.01); between genetically different groups (HP vs. HP X F and NP vs. NF) for IGF-1 (243 vs. 298 and 370 vs. 474 ng/ml, respectively; P < 0.01); and between different ages for IGF-1 (values increasing with age, with highest values at 12 and 14 months; P < 0.01) and cortisol (highest values at 14 months; P < 0.01). It appears from this study that the double muscling condition is accompanied by a lower concentration of insulin and IGF-1 in Piemontese and in crossbred HP X F bulls. The most interesting aspect is that IGF-1 concentrations, which are age dependent, show significant differences due to breed both in normal and double-muscled animals. (C) 2001 Elsevier Science B.V. All fights reserved.