Hemsworth, P. H., Barnett, J. L., Hansen, C. et al. 1986. Effects of social environment on welfare status and sexual behaviour of female pigs: Effects of space allowance. Applied Animal Behaviour Science 16, 259-267.

This study examined the effects of housing groups of adult female pigs (6 pigs per group) with a space allowance of 1, 2 or 3 sq.m per pig. .. There was a significant increase in plasma free-corticosteroid concentrations when gilts were housed with a space allowance of 1 sq.m per gilt. The elevated free corticosteroid levels of gilt in the 1 sq.m per gilt treatment suggests that a chronic stress response due to crowding may have been responsible for the apparent impairment in the sexual behaviour of these animals.