An Udder Disaster

At the beginning of your upkeep, you may
pay {1}{g}{g} if you do, a target a Cow you control become a green white
base power and toughness
2/3 Cowceratops with trample or a green white
base power and toughness 3/2
Cowasaurus with Rampage 2 until this card
leaves the battlefield.
At the beginning of your end step you may pay
{3}, if you don't, sacrifice this card.