For decades, the Department of Agriculture has routinely conducted surprise inspections at zoos, breeding operations, research labs, and other facilities to evaluate whether they’re complying with federal animal welfare laws, and issue warnings or penalties if not.

Now the agency is testing another approach: ‘‘announced inspections.’’

In a letter sent last month to entities regulated by the Animal Welfare Act, an agency official announced the launch of a pilot project to explore whether letting some facilities know inspectors are coming ‘‘actually improves the efficiency of our inspection program and improves the humane treatment of animals.’’ The department has no plans to discontinue unannounced inspections, but is considering ‘‘blending’’ them with announced ones, wrote Bernadette Juarez, the deputy administrator of animal care in the agency’s Animal and Plant Health Inspection Service.

Giving advance notice could help ensure a facility’s attending veterinarian is present and coordinate ‘‘optimal hours’’ for the inspection, Juarez wrote.

An APHIS spokesman, who confirmed the authenticity of the letter, declined to make an agency official available for an interview. But the program appears to be part of a broader reevaluation of the inspections process at more than 10,000 facilities assessed by 103 agency inspectors. Earlier this year, the department solicited public comment on the possibility of considering third-party inspections as part of what it calls its risk-based system, which relies in part on a facility’s record of compliance with animal welfare laws.

Both ideas are unsettling to animal protection advocates, which say they would reduce accountability for an agency that has already come under fire for a lack of transparency. Early last year, the USDA abruptly removed all inspection records from its website, only to replace many with heavily redacted versions. Announced inspections, critics say, would be akin to police calling a possible crime scene before arriving to investigate.

‘‘It’s going to result in even fewer violations being detected,’’ said Delcianna Winders, a vice president at the People for the Ethical Treatment of Animals Foundation. ‘‘Things are going to be cleaned up, suffering and dead animals are going to be hidden, and we’re just not going to know what the real, day-to-day conditions of the facilities are.’’

APHIS has not advertised that it is weighing whether to allow announced inspections, and the pilot project was not identified in the Federal Register docket USDA opened on the prospect of weighing third-party inspections of animal welfare conditions. While Juarez’s letter said the pilot is targeted toward ‘‘certain situations involving certain facilities,’’ it did not clarify how those facilities would be selected.

As required by the Animal Welfare Act, the agency conducts inspections annually at research facilities and at least every three years at others, looking for things ranging from proper enclosures to trimmed hoofs to clean drinking water. The frequency of inspection depends on how well a facility has previously performed and other criteria that the agency does not specify. (PETA sued the USDA in March over its failure to respond to a public records request for this information two years ago.)

In October, a coalition of scientific research groups issued a sweeping report that recommended, among other things, that Congress reduce inspections to every three years and that the USDA consider AAALAC accreditation as a factor in its risk-based inspection system. In comments to the USDA, that coalition, the Federation of American Societies for Experimental Biology, said 82 percent of USDA inspections at research facilities in fiscal 2017 were free of ‘‘noncompliant items,’’ or violations, and 84 percent of violations ‘‘did not pose a direct threat to animal welfare.’’