Influence of separate feeding of calcium on nutrient digestibility, energy utilisation and performance of young broilers fed pelleted wheat-based diets

•The present study confirmed the previously reported Ca-specific appetite in modern broilers.•Feeding low Ca diets with access to a Ca source is advantageous in terms of growth performance.•When Ca sources are mixed in the diet, a substantial negative effect can be seen on P digestibility.•Provision of a separate Ca source may hold promise for reducing dietary P level in broiler chickens. Six broiler starter diets, based on wheat and soybean meal, were formulated to contain 1.1 2.0, 4.0, 6.0, 8.0 and 10.0g calcium (Ca)/kg. All diets were equivalent in respect of total and non-phytate phosphorus contents (5.4 and 3.0g/kg, respectively). The influence of dietary treatments on the growth performance, coefficient of apparent ileal digestibility (CAID) of nitrogen (N), starch, fat and phosphorus (P), Ca retention and apparent metabolisable energy (AME) in broiler starters was evaluated. A total of 288, one-day-old male broilers (Ross 308) were allocated to 36 cages (8birds/cage), and cages were randomly assigned to 6 dietary treatments. Birds were also provided with a source of Ca in a separate feed trough. Birds fed the diet with 1.1g Ca/kg gained more (P