Piglets on straw© Tim Scrivener

A trial looking into pig behaviour has found welfare and environment can influence “proactive” and optimistic behaviour or “reactive” and pessimistic behaviour.

This proves a similarity to human “cognitive biases”, in which judgement is influenced by mood and personality, say researchers at Newcastle and Lincoln Universities.

See also: Farm’s farrowing tent brings welfare benefits to pigs

In a world-first experiment, pigs were housed in two distinct environments to create positive and negative effects on moods in study that appeared in the journal Biology Letters.  

Two categories were used; pigs were either proactive or reactive.

The experiment

  • Pigs were weaned at 4 weeks
  • Commercial cross breeds PIC337 large white cross landrace
  • 24 males and 12 females were assigned randomly
  • Both environments had solid flooring, a slatted area and wooden blocks on chain
  • More enrichment meant deeper straw and more space (more than 0.62m sq/pig)
  • Ventilation and temperature controlled (28C, decreasing 0.5C daily to 19C

Proactive pigs

  • Positivity is characterised by more active conduct and a consistency in behaviour

Reactive pigs

  • Passive behaviour and being more changeable in responses.

Finding pessimistic pigs

Two bowls of feed were used in each environment, one containing sugar-coated sweets and a third containing coffee beans, thus providing a positive and a negative outcome respectively.

A third ambiguous bowl was introduced and researchers observed whether pigs approached it expecting more sweets or ignored it.

See also: Danish loose-housing trial puts emphasis on welfare

Professor Lisa Collins, University of Lincoln’s School of Life Sciences said: “The results of our study clearly show that those pigs living in a worse environment were more pessimistic, and those in a better environment were much more optimistic.

“Importantly, this finding demonstrates that humans are not unique in combining longer-term personality traits with shorter-term mood biases when making judgements.”