Why is synthetic or naturally sourced astaxanthin added to farmed salmon feed?

Answer

To ensure the flesh develops the desirable pink color consumers expect

Astaxanthin is added to farmed feed because the vegetable-heavy diet naturally lacks the carotenoids found in wild crustaceans; this supplementation is necessary to achieve the marketable pink flesh color.

Why is synthetic or naturally sourced astaxanthin added to farmed salmon feed?
fooddietanimalfishsalmon