You guys do realize you can breed them right LOL
So here is how you can make a leather farm without crashing the server
Keep 4 cows at all times. They can pop out crotch fruit every 5 minutes. Babies take about 20 to become adults.
So just stay near your farm, feed them every 5 minutes, and then after an hour or so, kill everything except for 4 of them.
I am not worried about server lag from a cattle farm that is gone in a few hours, or even a full day.
Its the constant lag that it creates over time if we all have one.
Alternative Leather farm:
Get diamonds, obsidian, glass, dusts (all 3), a few chests
make an Energy collector, and energy condensor.
done, never want for any material ever again