Ozark,
With identical management, identical feeds etc. The parasite and disease load will be heavier on the southern animals, because of the warmth, the longer summer temps give more generations per year
I don't doubt this one bit. That is why we should have different gardening strategies. (not sure why this in a big font)
I mean how many dandelions can you grow
Only enough for my salad and no more.

All soil are not equal, but we do the best we can. It's far better to return the vegetation to the soil, then to remove and discard. I have over the years introduced [url=https://www.azomite.com/]Azomite[/url]to the soil. It has 70 active minerials and trace elements. Azomite can also be added to animal feed. Something like 10%. This is a mined product and has it's own issuses.
And it is not fair to say: Well, I don't deal with early frosts it must be your management... that is the equivalent of saying to a southern gardener... those bugs are your mismanagement, your poor gardening! I call foul, unfair! With identical management, the northern areas will still have later frosts in spring, earlier in fall, and the southern areas will have more bugs, and diseases to deal with... fact of life!
"It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change"
Can you point to the post that made these comments? I find it interesting. I didn't know we could control Mother nature. Well, we can sort of. I'm surprised that floating row covers are not being taken advantage of. They will do both. Raise the temperatures by 4 degrees, protection from light frost. Control insects and birds. I have not crunched any numbers, but I bet the covers are cheaper then insecticides over the long run. We need to adapt.
Gumbo has a wet garden at the moment, he will have disease issues due to this wetness, and likely fungus too, not his fault, not his mismanagement... just fact of life! Whether he tills, or is a permie guru, the location does affect lots of issues! Would I trade less bugs and disease for more cold weather and snow and ice? No way! I would consider moving farther south, farther into bugs and disease, but not north into more cold and snow.
I'm sorry about the whole Katrina problems. Under 3 plus feet of water. sheesh. Not his fault, but he is living on the planet. We are the problem. Global warming is a whole nother subject.
Gumbo should not be tilling wet clay soil. One of the quickest way to destroy soil structure and create hardpan.
Also when you say North. You need to more specific. The Northwest has far less rain and snow then Northeast.
Eric