Meat production is a complex process in which the absorbed nutrients are directed under hormonal control towards muscle growth. According to consumer's standards a high quality carcass should contain a large proportion of lean meat and a small amount of fat. In Western Europe, cattle meat is produced both by beef and dairy breeds used as pure breeds or breed crosses. Holstein and Belgian Blue - double muscled type - are 2 extreme breeds in terms of meat production. The aim of the present experiment was to relate animal performances with plasma hormones and metabolites in these 2 breeds

Six Holstein bulls and 6 bulls from the Belgian Blue - double muscled type - were used. They were 4 and 6 months old respectively on the beginning of the experiment. They were kept in metabolism stalls. The fattening diet was based on dried sugar beet pulp supplemented with soja bean meal, rolled barley, hay, minerals and vitamins. The amounts of feed given were weighed daily. Live weight was recorded once weekly.