The invention relates to methods of increasing bone strength in an animal, preferably a mammal. In one aspect, the methods provided by the invention involve administering to the animal strontium and a phytase enzyme. In another aspect, methods are provided for treating or preventing osteoporosis in a subject, the method comprising administering to said individual a phytase enzyme and strontium. Also encompassed are animal feed compositions comprising a phytase enzyme and supplemental strontium and a dietary supplement composition for administration to a human, the composition comprising a phytase enzyme and supplemental strontium.