Abou-Ismail, U. A., Darwish, R. A., Ramadan, S. G. A. 2014. Should cages of laboratory rats be enriched physically or socially? Global Veterinaria 13(4), 570-582.

Experiments of environmental enrichment usually compare between group-housed rats in enriched and unenriched cages or between group-housed rats in enriched cages and single-housed rats in unenriched cages. This bias is mainly to maximize the chance of enrichment both socially and physically. The present study was designed to assess whether the addition of physical and social environmental enrichment causes different effects on the behaviour, performance and welfare of male laboratory rats from weaning through adolescence. 30 newly-weaned male Wistar rats were housed in either standard cages (SC), physically enriched cages (PEC) or socially enriched cages (SEC) for five consecutive weeks. Animals were received in three batches and each experimental treatment was replicated two times within each batch. Results revealed that rats housed in the (PEC) displayed higher levels of measures suggestive of improved welfare such as sleep, grooming, feeding, moving, exploration, body weight, weight gain, relative weight of thymus, spleen and testes and being in-the-open part of the cage and lower levels of measures suggestive of compromised welfare such as stationary, bedding-directed behaviour and being under-hopper compared to rats in the (SEC). It appears that physical method of enriching conventional cages can have significant effects on behaviour and growth of laboratory rats and may therefore improve their welfare.