What makes deer meat taste gamey is the same thing that makes all meat taste gamey. A gamey quality comes from animals who have access to a more natural diet and have the opportunity to move about freely.  This usually happens in the wild, but some animals, like deer, are raised domestically but in a setting that more replicates the wild environment. As such, the meat from these animals – whether they are in the wild or grown domestically – gets a high iron content from all the exercise animals get and from what they eat. This lends itself to a gamey taste.