There hasn't been any problems with farm chunks unloading before, or at least I've not been told about it.

oh ok it happened in my single player not sure if bukkit fixes that but still the pets will despawn

Bukkit isn't involved with singleplayer, that's a total different list of coding, the chunk loading is a Minecraft problem. I don't play singleplayer so I wouldn't be able to help here .

If we had a chunk loading problem I think that would been fixed very easy by the Admin team, nobody has complained before this post about losing their Cats, Dogs, Cows, Chickens Etc

And if this plugin were to be added it would lag the server really bad, as the plugin is called "Chunk-Loader" it loads
more chunks and therefor brings more lag to the server.

They would be disappearing because of Clag, which every so often will erase all the mobs on the server. This is to prevent there be an overabundance of mobs everywhere completely lagging the server. Mob spawns in 1.3 have been completely broken, and they spawn too much and the spawn limits don't stop them from spawning for some reason.

So therefore to keep mobs being able to spawn we had to implement Clag so that we have a way to regulate the spawns, I'm assuming at least until spawns can be fixed, presumably in 1.4.

Well its 1.4.2 now and im wondereing if it is still broken