The CS in Flex Free is derived from bovine and porcine trachea, which is processed extensively to isolate a high purity fraction of chondroitin sulfates. In this way, additional resources are recovered from a renewable source. Genuine shark cartilage is not an efficient or economical source of natural body lubricants. It does contain certain antiangiogenic proteins that have been the subject of worldwide cancer research. Because these proteins inhibit the development of new blood vessels, shark cartilage is not recommended for broodmares or growing horses.
Sharks face intense environmental pressure, and several species are now endangered.
Under these conditions, we do not feel it is wise to be feeding it to horses, when cheaper and more appropriate renewable supplies are available. While some folks still think that chondroitin sulfates have not been proven to be absorbed from the diet, researchers have reported for over forty years that absorption and post-absorption activity occurs in the species tested. In fact, recent US research has confirmed earlier findings from Europe and Japan. Unlike glucosamine, which seems to be absorbed at the same high rate in all species tested, chondroitin sulfates show markedly different absorption profiles from one species to the next. I want the best for my horse.