What version are you on? Should be next to the milk tank at the co-o
im on the non maize plus version. i only tried with one tanker but it works on everything else. not a huge deal i just put down a sell everything point and made it work. however ive encountered other issues with the cows. mainly whenever i sleep through the night 200 cows go through 80,000 liters of feed, not a huge issue. also the grass fields next to the cow lot. i plowed up and created fields, sowed alfalfa and when i slept it converted back to non usable grass field.