General staffs had figured out the max radius of action from supply points using horses without local supply (foraging/grazing) before Napoleon.
How far can you go before the the cart is just hauling food for it's own horses?
And extensions of that, Like the artillery cannot use it's horses to move food.
Horses are not trucks, they need to be feed every day. They also need more than grass or horses get sick and weak fairly soon. If you are depending on local fodder, you have to give the horses time to eat/graze and that is not time that they are "marching" or even resting. All of this was well known. Also how much water was needed and if water was available on the routes chosen in sufficient quantities. And that is clean water, not water that has been churned to mud by the first 900 horses at the watering hole. And in winter???
You also need a sizable support system. The Horses need shelter in bad weather, they need vets or at least some vet training. They need farriers (horse shoes and mobile blacksmith shops).
There were also different kinds/type of horses. Cavalry horses don't pull wagons well. Large draft horses are too specialized, They don't handle bad weather and poor food well.
By WW I most of this was well known. By WW II the Germans had thousands of men assigned to horse care. There are books written about it and how many mobile horse/vet hospitals there were. Some had a capacity of hundreds of horses and were transportable by rail.
You can't take a truck mechanic and make him horse handler/first line care giver any more than you can take a good horse handler and just drop him into a truck mechanic slot.
Both horse and truck transport systems can be overloaded and break down. And you can't change from one to the other in a few weeks or months in the middle of a campaign.
The German army had horse breeding programs and arrangements with horse farms/suppliers as did most other countries that used horses.
A big change was in WW I when the Army took so many horses from German agriculture that it crippled food production. While they knew how far you could travel with horses and how far they could travel per day or week very few wars until WW I lasted over the winter or for several years. With a short war some of the horses were returned after the summer campaigns and the long term civilian disruption was not as well studied. The British had similar problems in WW I. The whole subsidized truck thing where civilian truck owners were paid a yearly fee for their trucks so the Army could take them in case of need came from a long history of similar systems for calling in civilian horses in time of need (so the army didn't have to maintain the infrastructure of vets, care, shelter, etc in time of peace.) In time of war you need to leave a fair amount of the Breeding horses in place to ensure replacements. Deplete the breeding stock and you start running out of horses in the 2nd/3rd years.
truck logistics were relatively new in WW II, Most logistics had moved by rail in WW I with only short distances covered by truck/tractors. And WW II trucks were rather different than WW I trucks in terms of maintenance and life.