Most papers on this topic date to the 1920s and 1930s before feed quality was effectively upgraded. But here's one in ResearchGate from 1977 that covers some of the lit: Article Susceptibility of a Dwarf Strain of Chickens to Rickets
Have you done a systematic review on rickets in chicken? If the answer is no, I would like to suggest that you first do a review of this interesting topic and find out what is the current knowledge on this issue and what would be the next step. In other words, you can establish the study design.