[Evolution of plasma concentrations of testosterone and insulin-like growth factor I during the peripubertal period of cattle catheterized at the hepatic level].

To study endocrinal control of growth development in cattle during puberty, major hepatic vessels were cannulated in 8-13 week old Holstein male calves. In our experimental conditions, chronic hepatic cannulation with "grey" polyurethane catheters was performed for a long period (more than 65 d) without any rejection problems. A physiological washing solution containing at least 5 x 10(5) IU/l heparin-lithium was required to prevent cannula occlusion. Moreover, echography was utilized for rapid and accurate introduction of catheters into the vessels. With chronic hepatic cannulation, we have observed that plasma testosterone and insulin-like growth factor I (IGF-I) levels in cattle were lower in portal and in portal and cava veins respectively than in the other vessels. Our experiment has also shown that average plasma testosterone and IGF-I concentrations sharply increased at puberty to reach adult values. However, no relation was observed between these two hormones during the pubertal period. In conclusion, both testosterone and IGF-I plasma levels can be used as predictive factor of age at puberty but more investigations are needed to establish standard values for each breed.