Scented straw increases play behaviour in pigs

The research team, whose scientific article has been published in the journal Animal, spent two years studying pigs’ behaviour when provided with scented straw. They also examined whether various welfare indicators, such as tail injuries, ear injuries and body soiling, were reduced as a result of the scented straw.

– We wanted to highlight the whole picture with this study; not only how to avoid poor welfare, but also if suitable biological interventions can positively influence pigs, for example by encouraging natural behaviours such as play and exploration of their environment, says Maria Vilain Rørvang, Associate Professor at the Department of Biosystems and Technology at SLU and lead author of the study.

Pigs played more 

The study included 1,600 pigs from 10 weeks of age until slaughter. The scented treatments consisted of essential oils with fragrances such as lavender, aniseed, and pine. Four different treatments were tested: two involving straw scented at different intervals, and two control treatments using unscented mineral oil.

– We found clear statistically significant evidence that the pigs were more engaged with the scented straw. They sniffed it and played more with it, and also with each other. We observed these results even though there were no other clear improvements in negative welfare indicators, such as tail and ear injuries and body soiling.

Maria Vilain Rørvang explains that pigs have a well-developed sense of smell and a natural need to explore their surroundings using their snouts. Introducing novel scents may also help prolong the enriching value of straw.

– It is fascinating to see how the pigs’ curiosity is stimulated when they are exposed to scents they do not normally encounter. Their play behaviour, such as picking up straw in their mouths and running around in a way that resembles dogs playing may also be an indicator of a positive emotional state, she says.

Natural behaviours in focus

The researchers believe that the increased interaction with the straw and the rise in play behaviour suggest that scented straw could be a promising way to stimulate natural behaviours and improve pig welfare in commercial production systems.

– In commercial pig production, keeping enrichment materials such as straw interesting over time is a challenge, and our results suggest that scenting may be one way to sustain pigs’ interest in the material, says Maria Vilain Rørvang.

At the same time, further studies are needed to investigate how these effects may vary across different production environments and stages of production.

The study relates to the United Nations Sustainable Development Goals, particularly Goal 12 on Responsible Consumption and Production, by exploring strategies to improve animal welfare within commercial livestock production.

The study was funded by Formas.

Read the scientific article: “Olfactory enrichment – effects of odorised straw on exploratory behaviour, straw engagement and play in finishing pigs” in Animal.