Here’s more proof that pets are big business. Brentwood-based Tractor Supply Co. has paid about $116 million for Petsense, a speciality retailer of pet supplies and services. Petsense has 136 stores in 25 states. According to a news release, it will now operate as a Tractor Supply subsidiary out of its current headquarters in Scottsdale, Arizona. Tractor Supply aims to grow the Petsense store base at an annual rate of 15 percent to 20 percent.