Why should different groups of livestock be kept separate before slaughter?

In the context of meat processing, keeping different groups of livestock separate before slaughter is a critical practice for minimizing stress in the animals.1

When livestock experience physical or psychological stress, it triggers biochemical changes in their muscles that can lead to significant postmortem quality problems. Specifically, mixing different groups of animals can induce stress, which is a primary factor in the development of pale, soft, and exudative (PSE) meat or dark, firm, and dry (DFD) meat. These conditions negatively affect the texture, water-holding capacity, and appearance of the final meat product.213

By preventing the mixing of groups, along with maintaining adequate ventilation and avoiding overcrowding, processors can reduce preslaughter stress and ensure higher product quality.1