Biochemical analyses
Samples in lithium heparin were centrifuged at 3000 rpm for 10 min on arrival at the laboratory and the plasma was separated for biochemical analysis. Plasma was stored frozen at − 24°C until analysis. Determinations of 13 parameters were made in sampled birds: Albumin (Bromocresol green method), Globulin (Biuret method), Urea (Urease–GLDH method), Glucose (GOD-PAP method), Cholesterol (Chol. esterase chol. oxidase–Trinder method), Calcium (o-cresolphthalein complexone reaction), Aspartate aminotransferase AST (IFCC technique), creatinine kinase CK (IFCC technique), Uric acid (Uricase–Trinder method), Lactate dehydrogenase LDH (Pyruvate–lactate method), Sodium (Indirect ion selective electrode), and Potassium (Indirect ion selective electrode).
All biochemical analyses were conducted under ILAB 600 (Instrumentation Laboratory UK, Cheshire, UK) according to manufacturer instructions. For some samples, there was insufficient sample volume to realize analysis of all the biochemical metrics. The laboratory’s quality control was to run daily internal quality control material and to peer review the results with other laboratories by using two external quality assurance schemes: the Randox International Quality Assessment Scheme and the American Veterinary Laboratory Association.