The experimental protocol was approved by the Italian Ministry of University, and the study was conducted in compliance with the requirements of the Animal Ethics Committee of the University of Camerino. Animals were slaughtered according to European Union Regulations (Council Directive 93/119 EEC). Twenty-eight male entire lambs of Fabrianese breed,born on the same farm located in the Marche Region within a 4-day period and weaned at an average age of 30 days, with similar live weaning weights (14.5 ± 1.34 kg)were selected from a herd of approximately 100 lambs, then allotted in collective pens (seven animals per pen)and fed a diet based on oat hay (78 g CP/kg DM and 10.3 MJ ME/kg DM) supplied ad libitum once daily and concentrate (179 g CP/kg DM and 12.4 MJ ME/kg DM) supplied ad libitum once daily, too. Fourteen lambs were slaughtered at an age of 60–65 days (2 months), selected on the basis of their live weight, the remaining 14 were slaughtered at a final age of 150–155 days (5 months).