Purina? Layena? layer feed provides all 38 nutrients laying hens need once they?re 18 weeks old and laying eggs. Feeding Purina? Layena? layer feed to your hens provides you with delicious and nutritious eggs that your family and community can enjoy. The exclusive Purina? Oyster Strong? System strengthens eggshells with added calcium from oyster shells, Vitamin D and manganese.