This study investigated how housing hygiene conditions affect mesenchymal stromal/stem cells (MSCs) in pigs with different feed efficiency levels. Researchers housed 12-week-old pigs from high and low feed efficiency lines in either good or poor hygiene conditions for six weeks, then analyzed MSC populations in fat and muscle tissues. Key findings showed that poor hygiene conditions altered the proportions of specific MSC populations in both tissues, but the effects varied by tissue type. In muscle, one particular MSC population (CD45-CD56+CD34+CD140a+) increased under poor hygiene conditions. In adipose tissue, different MSC populations responded differently - one increased while another decreased under poor conditions. The study suggests that environmental stressors like poor hygiene can influence stem cell populations in tissues, which may impact how animals develop lean versus fat mass during growth. This has implications for understanding how housing conditions affect pig production efficiency and body composition.