Abstract
Environmental enrichment is one of the methods used to reduce conflicts at weaning, which erupt when mixing unknown litters and are known to negatively affect growth and welfare of piglets. Here we aimed to test a simple approach of increasing the amount of existing enrichment objects to mitigate post-weaning aggression. The experiment comprised ten groups of piglets (five controls, five tests) with 3-4 litters weaned in each of them. In the control group, a red hanging plastic object (biting ring) and a piece of spruce wood (7 cm × 7 cm × 30 cm) were used for enrichment. In the test group, the enrichment was multiplied according to the number of weaned litters (one toy and one piece of wood was provided per each mixed litter). On days 1, 3, 5, 7 and 14 after weaning, behaviours (negative social behaviours, pen equipment-directed and enrichment-directed behaviours) and injuries (on different parts of the body, tail lesions, lameness) were recorded. On day 21 after weaning, the overall welfare status of the piglets was assessed using the Welfare Quality(®) protocol for pigs. A significant (4-fold) increase in the enrichment-directed behaviours was observed in the test group (p < 0.001). Consequently, there were 3.5 times fewer negative social behaviours (p < 0.001), 38-52% fewer injuries on different body parts (p < 0.001) and higher overall welfare status of the piglets in the test group. Adjusting enrichment to the number of weaned litters proved to be an effective solution to reduce aggression at weaning and improve piglets' welfare. The study provides important information on the use of enrichment material in commercial weaner pens and demonstrates the possibility of significantly improving pig welfare with low effort, input and cost.