Popular and commonly used offal includes rumen, leafy gizzard, heart, poultry stomachs, liver, kidney, lungs, spleen and gullet.
Rumen and leafy stomach are the stomachs of ruminants. Dogs in particular love green rumen, which is better fed raw because the smell of cooked rumen lingers for days and is only for strong human noses. The protein quality and digestibility are somewhat lower than with meat, because forestomachs contain more connective tissue and keratin. Some dogs therefore get flatulence. Green rumen and leafy stomach contain vegetable matter and therefore have some fibre content and more B vitamins.
heart and poultry stomachs and are almost pure muscle and therefore just as high in quality as meat. For the declaration of feed, however, they may not be called meat, because only skeletal muscle falls under this term.
Liver, kidneys and spleen contain around 20% protein and less than 5% fat, are highly digestible and rich in nutrients. Liver has the generally highest trace element and vitamin content of all offal. It contains considerable amounts of vitamin A, as well as iron, copper, vitamin D and vitamin B12. Spleen contains a lot of iron and kidneys are particularly rich in selenium.
Since vitamin A is toxic in very high quantities, we should warn against excessive or one-sided liver administration. As a rule of thumb, 0.5 - 1 g of liver per kilo of body weight is sufficient to cover the daily vitamin A requirement. Poisoning occurs when the requirement is exceeded by about 100 times, especially in cats.
Mouth and lungs are also rich in protein and are often used for cash rations, but also for canned food or in dried form as a treat. The protein quality is lower than with meat because - similar to rumen - the connective tissue content is higher. Flatulence would therefore not be surprising.