NB

Animal extract collagen is mostly absorbed from cow and chicken, and especially from pig. You can easily get animal collagen extracted from pig skin the most in local markets.
According to research, animal collagen is one seventh inferior to fish collagen when broken down by molecular weight. Collagen is only absorbed after it is broken down into peptides by digestive enzymes. The ability of breaking down collagen is equal to that of absorbing collagen. Thus, fish collagen is seven times more capable of breaking down collagen to be absorbed than collagen from pig skin.  It is well known that pork is more difficult to digest than fish. Collagen works in the same way. Also Fish raw materials without environmental pollution, does not give the fish a shot, pill, nor presence of mad cow disease, swine flu and other issues but bovine and porcine origin have. So it is safer to use fish as raw material to produce collagen.