Now, I know lamb doesn't come to mind when thinking of unusual protein sources, but lamb was one of those meats I rarely, if ever, ate. (lichenpaleolovingaip.com)
For example, there are many brands of dog food that contains unusual protein sources such as rabbit or venison — great for testing allergic reactions to other, more common proteins. (dogbreedz.com)
They have a great assortment of treats with unusual protein sources like Bison and Venison for Cody's sensitive stomach. (lessonsfromaparalyzeddog.com)