The Humane Society of the United States (HSUS) and four other groups have filed a lawsuit seeking lower speed limits on chicken slaughter.
At some plants the slaughter rate is 175 birds per minute.
The United States Department of Agriculture began allowing waivers in 2018 that enabled plants to speed up lines by about 25 per cent.
The HSUS said in its lawsuit filed this week that the waivers raise public health, animal welfare and worker safety concerns and that the USDA made the change without allowing for a period for public comment.
