Investigators also found conditioning, training, veterinary, and breeding equipment, indicative of animal fighting at Murphy's residence, records show.
Five more pit bulls were confiscated from a property in Townsend, court documents said.
Murphy, 51, pleaded guilty to nine counts of possessing animals for use in an animal fighting venture, in violation of the federal Animal Welfare Act, Levy's office said in a statement. Murphy's sentencing is scheduled for Feb. 27.
"This case marks the first time federal criminal charges have been brought in the District of Massachusetts under the Animal Welfare Act, underscoring the seriousness of these crimes and our commitment to holding those who engage in this abhorrent conduct accountable," Levy said in the statement. "We urge anyone with knowledge of animal fighting or abuse to come forward and report it."
A wiretap in 2021 between Murphy and dog fighters in Suffolk County in New York uncovered discussions about breeding, fight results, and injuries, according to a statement of facts filed in US District Court in Boston.
Facebook accounts revealed years' worth of evidence linking Murphy to private groups that discussed and shared photos of dog fights, as well as information for buying and selling fighting dogs, records show.
The photos and videos posted on Facebook showed a pit bull restrained in a breeding stand and dogs tethered to treadmills. One of the videos showed a live raccoon caged in front of a carpet mill to entice the canines to run faster and harder, federal prosecutors said.
"Mr. Murphy's actions represent the calculated cruelty and inhumanity that dogfighting embodies -- a barbaric practice that exploits and harms animals for entertainment and profit," Levy said. "Today's conviction brings an end to Mr. Murphy's reign of brutality and sends a clear message: dogfighting is a federal crime, and those who engage in this inhumane conduct will face justice."
Among the items confiscated from Murphy's residence were spring poles used to build a dog's jaw strength, flirt poles to entice chase, and break sticks to force open a dog bite, along with various types of treadmills, slat mills, carpet mills, and jenny mills to build stamina and muscle and develop endurance, Lev's office said.
Also confiscated was a dog bite sleeve, disposable skin staplers to treat wounds, injectable steroids, painkillers, a copy of "The Pit Bull Bible" and a leather dog collars with an "International Champion" engraved metal plate, records show.
"Dogfighting is a sadistic crime which subjects animals to cruel mistreatment for entertainment," Assistant Attorney General Todd Kim of the Justice Department's Environment and Natural Resources Division said in the statement.