Marin and Sonoma ranchers are leading a collaborative effort to launch a new mobile slaughter facility, taking matters into their own hands after the only regional slaughterhouse closed its doors to outside producers in January.

The group—called Bay Area Ranchers Co-op, or BAR-C—will tailor the facility to meet their needs, which have been increasingly dire since Marin Sun Farms ceased serving their labels at its Petaluma facility. To use one of California’s few other slaughterhouses,…