Here's why: thawed ground doesn't provide as much support as its more rigid, frozen counterpart. It's soft. It's full of water. One could even say the ground is currently willing to go with the flow. Every where you look in these parts right now, you can see where the land wants to be a riverbed; eagerly servile, it bends and shapes itself to accommodate the will of the water. The ground's not flat, nor is it still - things just don't work that way. Some fence posts handle the shifts with equanimity, but others fall right over.
When your fence posts fall over, your fence comes down, and when your fence comes down, your cows get out. These are dairy cows here, not the free-ranging beef cattle that you might imagine going for miles and miles out in cowboy country. If cows get out here, they're not going any place good. Yes, they're surprisingly adept at navigating pine-strewn, rocky woods, but they're not nearly as gifted when it comes to things like cars and highways. Dairy cows function on the presumption that everyone is Hindu; they blithely stroll down the pavement assuming everyone has a sacred duty to stop. You can imagine how well that works.
So when the fence posts come down, it's fairly important that they go back up again quickly. There are things that are easy. Setting fencepost in freshly thawed, saturated, rocky ground is not one of them. Cedar posts are said to be best, although post is a rather grandiose word for trees stripped bare and rough hewn into a spiky end. You'll learn new words watching the farmer do this work. None of them are safe for work. If you've got a tractor with a bucket, the job's faster: hydraulics makes life simpler, they surely do. But if you don't have a tractor, or if the tractor is otherwise occupied, or it too isn't doing what you need it to do when you need to do it, then it's you and a post hole digger and a sledge and your motivation to get the job done. Sometimes, you might not even have that much, but the cows don't care: if they can get out, they will get out - ad hoc fence posts, far more function than form, litter the landscape. You do what you have to do.
There's no amount of prior planning or preparation that will leave one in a place where the fences never need repair. Time and circumstance will bring your fence posts down. This is a thing that happens. Keeping the fences up takes work, and sometimes it's work you don't want to do. The weather might be sucky. It could be dark or cold or both. Sometimes early spring snow falls, just in case life wasn't difficult enough. It's back breaking, skin scraping, soul wearying work. It is undoubtedly no fun. But it is also undoubtedly necessary. When you need to preserve what you have, and keep those cows happy and healthy, safe and content, good strong fences are not optional. You don't realize how much work is involved in even the most humble, sorry looking fence until you watch it happening. But without the work, there is no fence, and then where would your cows be?
Where would your cows be indeed? Onward, upward, forward, beloveds. Here, it's time to make coffee. Other places, people are milking. I am so grateful not to be a dairy farmer right now, even if the art of the fence is not entirely unfamiliar to me. Onward, upward, forward in deed.