What I did was ensure I had a really large stockpile of catnip. I saw Winter was coming, and so I stopped spending catnip. That allowed me to have enough catnip to survive, even without farming.
But as you noted, you now have farmers. Once you get past four kittens, just living off of the stockpile of 5,000 isn't really enough. Most kittens should become farmers during winter, so that the rest of your population doesn't die off.
Another option is to build a barn or two, and make your stockpile even larger. The more barns you have, the more kittens you can support through a winter without farmers. Some later technologies allow you to build things that allow your kittens to require less catnip, and you can stretch it just a little bit further.
Generally, though, farmers are your best go-to for ensuring your population survives.
Looking at the code, the skills' information is as follows:
- Dabbling - No XP required - No bonus
- Novice - 100 XP required - 1.25% Bonus
- Adequate - 500 XP required - 2.5% Bonus
- Competent - 1200 XP required - 4.5% Bonus
- Skilled - 2500 XP required - 7.5% Bonus
- Proficient - 5000 XP required - 12.5% Bonus
- Master - 9000 XP required - 18.75% Bonus
Thus, a kitten who is splitting their time up between two jobs about evenly is going to still be under proficient when a kitten who'd focused on the same job all the time has made master. You're probably better off letting a small number of kittens focus on Farming continuously through the year; you won't get much benefit right away, but when they finally do make master, they'll be able to feed more kittens, especially with the upgrade later on that doubles how much bonus all skills give.
Even worse, any kitten who has skill in a job they're not currently doing, will slowly (very slowly) lose experience in that job. The effect of this is minor (five thousandths of an XP per second), but if you're idling for long stretches, it can stall progress if you're trying to teach a kitten two jobs.
In the end, though, it doesn't matter too much what you do this early in the game. Getting to master-level kittens takes a while, and swapping your kittens around won't stop them from making master in their jobs eventually; just slows it a little. Plus, once you get more Pastures, and the Hoe upgrades to your farmers, even a small handful of Dabbling farmers will be enough to feed a fairly large population through cold winters.
Best Answer
Catnip fields give infinite catnip. Therefor more fields is better. At least, that is my philosophy. I have 47 fields right now, and the next costs 2057. During spring I have no farmers and +1.5 catnip. During summer and autumn I need 1 or 2 farmers, depending on the amount of catnip I have to survive winter. During winter, I have most of the time negative catnip production, but I have a buffer (that was a tip from a previous question) so that does not matter very much. My buffer is now 3500, after a warm summer.
It's not mathematical my answer, but I try to upgrade my field when my buffer is more than twice as much as the price of the new field. In that way I still can survive winter and have as least as kittens possible on the farm.