Here is the full list of all 15 Cowpocalypse achievements.
Abduct your first cow
Abduct 42 cows in a single round
Get stunned for a total of 2 minutes
Abduct 100 cows before the timer reaches 60 seconds
Drop 10 cows by being stunned in a single round
Go a round without getting hit by a pitchfork
Don't abduct any cows for a single round
Abduct a cow while it is running away
Start the Game
Play 10 rounds
Travel in one direction for more than 20 seconds
Abduct 69 cows in a single round
Abduct 25 cows in a single round
Abduct 1000 cows in total
Drop 100 cows in total