Effect of 25-hydroxycholecalciferol supplementation with different dietary available phosphorus levels for broilers.

Based on the hypothesis that 25-hydroxycholechalciferol (25-OH-D 3 ) inclusion would optimise dietary mineral digestibility and ameliorate growth performance and bone mineralisation in available phosphorus (AvP) deficient-fed broilers, a trial was conducted to evaluate its effect in diets with different levels of AvP.Broilers aged 1 to 21 d were randomly assigned one of eight treatments, consisting of four dietary levels of AvP (0.45, 0.42, 0.39, and 0.36%) and with or without supplementation with 25-OH-D3 at 69 μg/kg of feed. All diets contained 100 µg/kg of vitamin D 3 (cholecalciferol).The addition of 25-OH-D3 resulted in higher feed intake and body weight gain, and lower FCR ( P  < 0.05) compared to non-supplemented diets, whereas AvP levels had a quadratic effect only on feed intake. There were no interactions between treatment factors.Increasing AvP levels linearly reduced ileal digestibility of Ca and P ( P  < 0.01) and supplementing 25-OH-D3 increased both Ca and P ileal digestibility ( P  < 0.05), without any interactions observed for ileal digestibility.There was an interaction, whereby 25-OH-D3 inclusion increased serum metabolites in broilers fed 0.36 to 0.42% AvP compared to non-supplemented diets ( P  < 0.001), whereas, at 0.45% AvP, diets with or without 25-OH-D3 had similar results.P content in bone linearly increased in line with AvP levels ( P  < 0.05) and supplementation of 25-OH-D3 increased ash bone content ( P  < 0.001).Broilers can benefit from 25-OH-D 3 supplementation combined with cholecalciferol in regard to Ca and P utilisation and vitamin D status, allowing for a reduction of dietary AvP levels down to 0.36% without impairing growth performance or bone status.