It is mostly an animal welfare concern. As the name implies it comes from slaughtered calves originally.

But those animals are already being slaughtered in slaughterhouses in thousands every day. I don't see the problem with using the intestines of dead animals.

Hello Doğan Tunalı

It is because of additional abilities. Calf intestine-purified CIP because of its inherently low thermal resistance and shelf-life has restricted applications.

Recombinant CIP is much more efficient. The reasons being as follows.

a. Rapid and irreversible heat inactivation which eliminates unwanted activity.

b. Efficient reaction requiring no additional supplements with much shorter incubation time.

c. Because of its high specific activity, less amount of enzyme will be required which would help save cost.

d. Storage stability is much improved for recombinant CIP with longer half-life of enzyme activity.

So, recombinant CIP because of its purity, stability, efficiency, cost-effectiveness and consistency would be preferred over calf intestine-purified CIP.

Best.

Malcolm Nobre If you could add references to your answer that would be both more helpful and credible. Nevertheless thanks for your answer.