Lactation Blood and Tissue Sampling Protocol

In both experiments, at day 20 of lactation, blood from Vena jugularis was collected 3 h after feed intake into heparinized polyethylene tubes (Sarstedt, Nürnberg, Germany), and plasma was obtained by centrifugation of the blood (1100 × g, 10 min, 4°C) and stored at -20°C pending analysis. At the same day, liver and skeletal muscle biopsy samples were taken percutaneously after anaesthesia by intravenous injection with 2 mg azaperon (Stresnil, Janssen-Cilag GmbH, Neuss, Germany) per kg body mass, 20 mg ketamine (Ursotamin, Serumwerke Bernburg AG, Germany) per kg body mass and up to 2.4 mg thiopental (Thiopental Inresa 0.5 g, Freiburg, Germany) per kg body mass as required for maintenance of anaesthesia. The biopsy procedure has been described recently in detail [36 (link)]. Liver samples were immediately snap-frozen and stored at -80°C pending analysis.