Mini goats are even harder to fence in than full sized goats. My boer cross buck and my Nubians have challenged fences the least, while the mini lamanchas go under or through them whenever they get a desire for something different.
I cannot speak to full sized goats, except one, as I have Nigerian Dwarf goats and one Lamacha. The only time the Lamancha has ever gotten out was when someone left a gate open. The minis will get out as long at they can fit through something, but they do not actively look for new ways to sneak out. If it is there, they will exploit it. If not, they wouldn't be bothered. But they are not sneaking out and then running off. They want to be with the herd, so they may slip the fence, but they stay along the fence line next to the herd. I do not keep any bucks, but what I understand is that mostly the issue is containing the bucks and keeping them away from the girls.
I have found them to be much more of a delightful and worthwhile venture than a frustration, are incredibly useful, highly companionable and intelligent. I have Nigerians True there is initial prep work in setting things up for them and in daily care required to keep them - I don't know that it is much different from keeping larger goats though they are smaller and easier to handle, can fit through smaller spaces as mentioned (and they will). They will also strip trees and ravage saplings, bushes, plants of most kinds as you likely well know so grazing areas need to be completely out of reach. If you want their milk (cheese, yogurt, soap) meat or wool, manure, and brush cleaning ways, and have dedication to their care, they are worth it!
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