The modern genetic breeds have increased productivity levels, improving the growth rate, profits and animal quality. As a result
nutritional requirements have been increasing as well.
Modern broiler chickens cannot make enough of the active hormonal form of vitamin D, (1.25-(OH)2-D3). When is fed, it is quickly hydroxylated to the active form. As a result, calcium, phosphorus and the divalent trace mineral abosorptions are increased.