Comparison of Cholecalciferol and 25-Hydroxycholecalciferol in Broiler Diets Designed to Minimize Phosphorus Excretion

Abstract

A study was conducted to evaluate 2 phosphorus regimes (NRC; modified), using diets supplemented with 1,000, 2,000, or 4,000 IU/kg of cholecalciferol (VIT-D3) or the equivalent amount of 25-hydroxycholecalciferol (25-OH-D3). Each treatment was assigned to 4 pens of 25 male broilers of a commercial strain grown in an open-sided house with sidewall curtains. At 21, 42, and 49 d BW and feed conversion (FCR) were determined. At 49 d, 5 birds per pen were killed to evaluate tibia ash of the right leg and incidence and severity of tibial dyschondroplasia (TD) of the left tibia. All remaining birds were processed at a pilot processing plant with agitated chilling and automatic evisceration to determine incidence of broken bones.No differences in BW were observed at 21 d due to dietary treatments. At 42 d, the BW of birds fed 4,000 IU/kg of vitamin D was significantly greater than birds fed 1,000 or 2,000 IU/kg; at 49 d the BW of birds fed 4,000 IU/kg of vitamin D was significantly better than that of birds fed 1,000 IU/kg with the BW of birds fed 2,000 IU/kg intermediate between these 2 levels. No significant differences in BW were observed at any age between source of vitamin D, phosphorus program used, or any interaction among or between vitamin D source, level, or phosphorus program. There were no significant differences observed for FCR and mortality at any age period or for tibia ash at 49 d. Birds fed 25-OH-D3 had a significantly higher severity of TD than birds fed VIT-D3, with no effect of vitamin D level and phosphorus program. Birds fed the modified phosphorus diet in combination with 2,000 IU/kg vitamin D had significantly lower incidence of TD than birds fed the NRC phosphorus diet with the same level of vitamin D. There were no significant differences among treatments for the number of broken bones during automatic evisceration in a pilot processing plant.