Duck is a powerhouse of nutrients some of them including selenium, zinc, vitamin B-3, and vitamin B-5. Both zinc and selenium are antioxidants that help boost your pups immunes system. Another great benefit of selenium is that it helps maintain a normal thyroid function. Duck is also a excellent all natural source of chondroitin, which helps promote mobility and agility by supporting healthy joints. Your pup is sure to love the taste of this duck jerky while also receiving all the benefits it has to offer. Barkworthies Duck Jerky is Additive free, chemical free, and preservative free.