What is the point of cattle?
Solution 1:
Cattle has two main uses. One of which may be more useful than others.
- They can provide food for your army
- They can often be used in quests from Village Elders, or your Marshal (if you are following them)
If you purchase some cattle, you can interact with them on the world map. You will be given two options: Butcher or Move the Herd (I don't remember the exact wording, but these are close).
By choosing to butcher the cattle, you will receive meat in your inventory which will provide food for your party until it is consumed, or spoiled. It's not the cheapest way to get food, but it can help if the town has nothing else.
By choosing to move the herd, you can corral them to another city, or to your Marshal's Army, should the Marshal (or Village Elder) ask for cattle. This will increase your reputation with whomever requested the cattle.
Solution 2:
One of the quests that you can get from a village is to bring them cattle. In addition to increasing the village's loyalty, I believe this also has an effect on its prosperity. When you have cattle they appear as a separate entity on the map. You drive the herd by moving your party towards it. The cattle will move generally away from your party (this takes some trial and error) until in range of the village, and then disappear. You can also overtake the herd, which will give you the option to stop them or drive them forward.
Solution 3:
More or less useless in vanilla, invaluable in some mods
Due to the way cattle is normally handled in the game, it is almost useless -- it "runs away" from you instead of following you, and, unless your world map speed is insanely high, which is not always the situation, it is very hard not to lose it.
Quests to deliver cattle are hence useless too. If you have a very small army, bandits are likely to try to rob you, and you can neither fight back nor run: you have the cattle. If you have a relatively strong infantry-based army, you will probably just have a hard time moving the cattle. For me, it seemed very annoying and time-consuming compared to other things you may do in the game. With a cavalry-based army, however, you are probably wealthy enough not to engage in cattle-related quests, and moving it with you makes you lose the advantage of speed, keeping the disadvantage of huge price of elite cavalry. Using cattle for sieges with a cavalry-based army is also not needed -- you shouldn't be using a cavalry-based army for sieges at all.
Also, you can't just click "move here" and wait for the computer to calculate the path for you, you have to manually control every single second of movement.
But if you use a mod that makes cattle follow you, and your speed is lower than the speed of the cattle, it may become invaluable sometimes. Why?
- It gives you a lot of food without using space in your inventory. Yes, some mods that allow you full access to the inventory of your companions make it not as valuable, but still.
- It doesn't spoil but allows you to have more variety of food, as raw meat spoils quickly.
It is especially important on sieges. In some mods going on assault is just as dangerous as it is in real life, so you have to take castles by hunger -- or at least you may attempt to. As towns and castles usually have huge reserves of food, they are impossible to take without cattle.
This strategy applies to vanilla, but you just don't need it there, because taking castles and towns by force is extremely easy and fast.