Do most mammals have the same nutritional needs as humans with regards to the ratio of each vitamin and mineral to each other (regardless of overall quantity).
For example, do any mammals have an extra requirement for vitamin A or for iron? Or do most mammals simply need every specific vitamin and mineral to fulfil x% of their nutritional intake, and it is the same for other mammals?
Every vitamin is used by bodies for some purpose. Depending on what a certain species has or do, you’ll need more or less of certain vitamin.
Animals with “bigger” brain will usually require more energy to make it work. Animals with large, constantly growing claws/teeths will need certain vitamin to keep growing them. Animals with hot blood will need more food for their heat.
Everything has a use, and what your body can do decide how much of each you need in average.
All species have their own nutritional needs.
The genetically closer 2 species are, the more similar will be their nutritional needs, but it’s still not the same.
Mammals are a large group with very distinct diets, so their nutritional needs are very distinct.
Our nutritional needs are more similar to chimp and primates in general.
All animals need energy (as carbs including fibers for the ones with bacteria that can ferment them, fat and/or proteins) and minerals (including nitrogen for the ones who have bacteria that uses nitrogen to make proteins). The ones that don’t have bacteria that produces proteins, must also eat proteins, but they don’t need nitrogen outside of the proteins.
Vitamin need aren’t shared by all animals.
In short, no, it varies. Most mammals can produce their own vitamin C, for example, so they don’t need to take it in with food. Humans (and other primates from the same group as humans, and also bats and guinea pigs) can’t make their own vitamin C, and therefore require to have it in their diet. In humans it’s due to a certain mutation that have broken our vitamin-C-making gene a long, long time ago.