Thank you for your reply.
Limestone is a natural source of calcium from sea creatures. Ground limestone is an AAFCO approved ingredient and is safe for use in pet foods.
Also be aware that Wysong products have been formulated by Dr. Wysong who has researched health, nutrition, and food processing for over 30 years and written 14 books on such matters. Wysong also has over 250 veterinary Clinical Consultants. We are not just a marketing firm, but a scientific and educational organization serious about health and with our own manufacturing facilities.
To better understand pet food and the safety and toxicity of ingredients, please review the links below.
Also, as per the Optimal Health Program
™, it is always wise to vary the diet as you say you have been.