The Germans were very sophisticated in "combined" operations, that is, in using airpower and tanks to attack behind the Soviet lines. That's what gave them the advantage in the early part of the war.
Ultimately, their mobile advantages could only be fully exploited by infantry And here, the Germans had far fewer advantages. For instance, during the 1944 counterattack of Operation Bagration, the Soviets enjoyed U.S. "Lend Lease" trucks to take maximum advantage of their breakthroughs. But apparently, the Germans had far fewer trucks, or other motorized transport, and relied on, yes, horses. As a result, during the early days of the war, large numbers of Soviet troops escaped from "pockets" because the Germans could not close the gaps between fast-moving armor and slow moving infantry.
Likewise, the Germans had major supply problems. There were trunk rail lines through the Soviet Union to only parts the front, and from what I understand, "lateral" communications were quite poor. These gaps were largely filled by horse transport, with the Germans being "glad" to capture U.S. Lend Lease trucks because their own were inferior in quality and quantity.
So how dependent were the Germans on horse transport? (My understanding was that the Germans were actually quite "primitive" in this regard compared to the Americans, British, and (later) Soviet armies which is one reason why they lost the war.) And given constraints on fuel and manufacturing capacities, did the Germans have any choice but to be so highly dependent on horses?