One objection, from an animal welfare perspective, against in vitro meat, is the fact that current blood serum is used to feed tissue cultures. Blood serum is a popular growth medium, because it contains the substances needed to culture cells ex vivo.
The problem with blood serum as growth medium is that animals has to be slaughtered. Without an alternative for this growth medium, cultured meat is unlikely to become widely available. Not in the last place because blood serum is quite expensive.
Klaas Hellingwerf from the University of Amsterdam, is working on an alternative growth medium derived from algae. If this inquiry succeeds, then in vitro meat can really become animal-friendly