Anizoba N W, Ugwu S O C, Ikeh N E, Uzochukwu I E, Orazulike O F and Machebe N S 2022 Periwinkle shell as an alternative calcium source on performance and egg quality of layer hens. Livestock Research for Rural Development. Volume 34, Article #2. Retrieved , from http://www.lrrd.org/lrrd34/1/3402nnenn.html