Exclusion / inclusion criteria.

Exclusion:

Not primary research. Not in English. Not relevant to PICO question: Study of other species such as guinea pigs. Outdoor housing systems. Early socialisation is not the sole intervention in treatment group (for instance: if the treatment group has two types of enrichment implementing at the same time, toys + socialisation, the study will be excluded). Piglets were not regrouped with unfamiliar piglets after weaning. No behavioural, physiological or growth performance outcome of weaning stress was measured post-weaning. Not controlled trial studies. Not accessible by online databases (University of Sydney institutional access).

Inclusion:

Primary research. In English. Relevant to PICO question: Species, pigs. Life stages: Piglets pre-weaning to post-weaning. Indoor housing systems. Comparison of pre-weaning socialisation with non-littermates vs no pre-weaning socialisation with non-littermates. Socialisation is the sole enrichment condition in the treatment group. Measured a behavioural and/or physiological and / or growth performance outcomes relevant to weaning stress when regrouped with unfamiliar piglets post-weaning. Peer-reviewed. Controlled trial studies. Accessible by online databases (University of Sydney institutional access).