Olfactory enrichment – effects of odorised straw on exploratory behaviour, straw engagement, and play in finishing pigs

Abstract

Effective provision of enrichment is challenging in commercial pig production due to costs and practical aspects. This experiment tested whether odorised straw could enhance straw engagement and improve welfare on a commercial farm. It involved 1 600 pigs, from 10 weeks of age to slaughter, housed in pens of approx. 10 littermates. Eighty pens were assigned to one of four treatments: Odorised straw provided in a rack with odour changing (1) weekly or (2) every weekday, or odourless straw (3) in a rack or (4) on the floor (empty rack). The remaining 80 pens served as controls (straw provided on the floor, no rack). Odorised treatments were essential oils (lavender, aniseed, ginger, thyme, or pine), and the odourless treatment was mineral oil. Clinical welfare scores (tail damage, ear damage, body soiling) were scored weekly, and behaviour was recorded (weeks 5, 7, and 9). Data collection included straw engagement duration, relative interaction with straw and pen inventory, play (locomotor, social, straw-related), and rubbing and rolling behaviour. Clinical welfare scores were not significantly affected by treatment. Tail damage and body soiling worsened over time (P < 0.05). Compared with odourless straw, odorised straw significantly prolonged straw engagement (P < 0.05) and significantly increased play and rubbing and rolling (P < 0.05). Relative straw and inventory interactions did not differ between treatments (P > 0.05). Increased straw engagement and play behaviour suggest that odorised straw is a promising enrichment strategy for enhancing pig welfare in commercial production systems.