ENON VALLEY, Pa. — William Kolehmainen uses his smartphone to move his cattle from paddock to paddock. Kolehmainen Cattle CompanyKolehmainen grew up less than a mile down the road on a grain farm in Enon Valley. The farm the couple owns today was Kolehmainen’s uncle’s dairy farm; Kolehmainen started working there in third grade, helping with various tasks during the summertime. How the GPS collars workThe Kolehmainens got the GPS collars in March after reading about them in a magazine and online. When the cattle get within 6 feet of the virtual GPS fencing boundary, they will hear a loud buzzing sound as a warning.