Effects of supplementary concentrates on growth and partitioning of nutrients between different body components in steers fed on grass silage at similar levels of metabolisable energy intake

A comparative slaughter experiment was carried out to examine the effects of feeding either grass silage alone or a mixed diet of silage and concentrate on animal performance and the partitioning of nutrients between lean and fat deposition in steers. Eighteen Hereford×Friesian steers were randomly assigned to two dietary treatments; grass silage only (S) or a mixture of grass silage and a barley/soya bean meal concentrate (80[ratio]20 on fresh basis) in the ratio of 60[ratio]40 (on a metabolizable energy basis; SC), and to one of three target slaughter liveweights, 250, 350 or 500 kg. Metabolizable energy (ME) intake was maintained at 800 kJ ME per kg metabolic liveweight (kg0·75) per day. The relationships between chemical composition and empty body weight (EBW) at slaughter were assessed using allometric equations (logey=logea+blogeEBW). When assessed across the slaughter weights, supplementing silage with concentrates resulted in higher rates of liveweight (P