Two great options for your "best friends." (1) Beef liver "Crack for Dogs" which make for great little dog treats, and (2) Pet food supplement with ground beef, heart, and liver to add to you dog's (or cat's) meal for added raw food nutrition and delicious.
The beef liver in each of them includes (1) vitamins and minerals (A, B-2, B-12, Zinc, Iron, Selenium) and (2) essential amino acids for healthy body repair and maintenance.
Let your little buddy give these little gems a try and they (and you) will never look back. Cheers!