Again, that's a cultural (pastoral nomadism vs settled society) question, not a question of access to natural resources.
Doubly so because a large part of the cultural difference was between traditions leaning toward heavy cavalry (larger, more powerful horses that required vastly more (and higher quality) fodder that steppe grass just could not provide), versus the short, stocky Mongolian horses built for endurance and able to live on steppe grass alone - one horse was suited to nomadic pastoralism, another to settled heavy cavalry warfare. The European could not have raised more of their horses on the Steppe (actually, they would have raised even less), and the Mongolian could have raised even more horses if they had been allowed to practice their pastoral nomadism on rich farmland rather than semi-arid grass.