All Massachusetts dairy farms are 100 percent free of bird flu, state officials announced on Monday.

At least 14 states across the country since March have herds that have tested positive for avian influenza, the Massachusetts Department of Agricultural Resources said.

Massachusetts is the first state to test dairy herds and have 100 percent negative results, the department said in a statement. Officials said they decided to test the herds to “protect public health” and demonstrate the safety of food from Massachusetts farms. In August, inspectors went to all 95 licensed dairy farms in Massachusetts to collect and test milk samples, the statement said.

“Massachusetts dairy farmers follow stringent safety protocols and take great pride in producing the highest-quality products,” said Massachusetts Department of Agricultural Resources Commissioner Ashley Randle. “That hard work protects all of us, and these test results demonstrate how supporting local agriculture and sourcing food from Massachusetts farms can keep our food supply strong and resilient.”

When avian influenza, or bird flu, affects a lactating cow, it can result in an “abnormal appearance of milk,” according to the American Veterinary Medicine Association. In some cases, it affects the cow’s appetite and reduces milk production. Some dairy farmers have contracted bird flu by coming into contact with unpasteurized milk from infected cows, state officials said. No human cases have been reported in Massachusetts.

“Pasteurization kills the virus and renders it safe for human consumption,” the state’s Department of Agricultural Resources said.

David Shepard, President of the Massachusetts Association of Dairy Farmers said in the statement he was “grateful” for the government assuring the safety and security of the Massachusetts dairy business.