The only concern is that the fat in grain finished animals is relatively evenly distributed throughout the meat, rather than being in a layer on the outside. It is easy to trim the fat from grass fed animals. In addition, there is some suggestion that grass fed animals have more of a particular form of fatty acid which has particular health benefits. Given the prevalence of low level iron deficiency in Western countries, it is primarily important to eat red meat. Grass or grain fed is a secondary and relatively unimportant consideration.
Organ meats are the most prized parts of a dead animal in all hunter gatherer cultures.
Organ meats are repositories of huge amounts of vital vitamins and minerals in a natural form. Today, we can buy organ meats as and when we want. Be sure livers you buy are form a young animal, as there is the issue of accumulation and concentration of the heavy metal cadmium in liver tissue when the animal is more than two years old. This is due to the cadmium content that naturally occurs in some important phosphate fetiliser sources. This major, if not primary, source of food is now unavailable, except perhaps for jungle fowl, ducks, and quail.