I am pretty certain the enzymes are still there, they have to be present ready and waiting for the first feed to make it's way down the gullet.
If nothing else, it does no harm to try.
Edit, Google saves the day!
No problem.
http://agris.fao.org/agris-search/search.do?recordID=YU9100139
There is some difference in the chymosin activity of calves which were calved during different seasons of the year. There is no difference between the chymosin activity in the rennet content of live or stillborn calves
https://en.wikipedia.org/wiki/Chymosin
Chymosin /ˈkaɪməsᵻn/ or rennin /ˈrɛnᵻn/ is a protease found in rennet. It is produced by newborn ruminant animals in the lining of the fourth stomach to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption. It is widely used in the production of cheese.