When I called my vet about using Lutalyse to abort an accidently bred 4 month old heifer he told me to use 2cc Estrumate i.m. at 28 and 42 days post breeding. I read here that 5 ml Lutalyse will abort a pregnancy up till 100 days. My sister keeps Lutalyse on hand because she breeds horses, which my vet knows. I feel inclined to use the lutalyse rather then buying Estrumate, but am wondering why the vet would recommend Estrumate instead?