Strategies to manage tail biting in pigs housed in fully-slatted systems

EU Council Directive (2008/120/EC) prohibits the routine practice of tail docking to control tail biting in pigs, yet most pigs in Europe are still tail-docked. This is primarily due to a lack of effective solutions with the least economic impact for the producers, especially in fully-slatted systems. This PhD project aimed to find strategies to manage tail biting in pigs housed on fully-slatted floors, using enrichment and dietary strategies. The first two experiments started with identifying suitable materials as enrichment for docked pigs housed in fully-slatted system. Pigs’ enrichment use was compared between four different wood types; beech (Fagus sylvatica), larch (Larix decidua), spruce (Picea sitchensis) and Scots pine (Pinus sylvestris L.), and also between wood types (beech, larch, spruce) and a rubber floor toy. Pigs were consistently observed interacting with the spruce more frequently than the other wood types in the two experiments, and the rubber floor toy also generated a similar amount of interaction from pigs as the spruce post. No carcass damage was found which could be directly related to using dried wood sourced from a commercial sawmill. The next experiment used a single enrichment item and different fibre levels in the diet to rear undocked pigs. In a 2×2×2 design, the pigs had either: A) a standard (weaner 3.7% finisher 5.9%) or high fibre (weaner 5.3% finisher 11.6%) diet; B) a spruce post or a rubber floor toy as enrichment in the weaner stage; C) the same/alternated enrichment given in the finisher stage. During this experiment a high level of tail biting was recorded (n=26 tail biting outbreaks), and a substantial number of pigs were removed temporarily or permanently from their home pens due to tail biting. Pigs fed with a high fibre diet had worse tail damage score and performed more tail biting. Pigs which had the floor toy in the weaner stage and wood in the finisher stage had slightly lower tail lesion scores. Pigs receiving the floor toy interacted with the enrichment more frequently overall. This study showed that higher dietary fibre in a relatively barren environment did not help reduce tail biting or tail lesions Moreover, a single enrichment item, which was preferred by pigs in the previous studies, was not enough in a group of 14 pigs to control tail biting, and thus the quantity of enrichment may be important factor to consider. In the final experiment, a 2 × 3 design was used to further investigate the effect of A) an enriched/barren environment during farrowing and B) three enrichment management strategies post-weaning, based on the frequency of replenishment (“Low”: on Monday/Wednesday/Friday; “Medium”: once daily; “High”: ad libitum). All pens received the same enrichment (8 items/12 pigs, including an elevated rack supplied with fresh-cut grass). The average daily gain in the finishing stage was slightly higher in “High” than “Low” pigs. “Low” pigs also performed more damaging behaviours (tail/ear biting, belly-nosing, mounting, other biting and aggressive behaviours) than “High” and “Medium” pigs. No difference in lesion scores was found between treatments. Although sporadic tail biting outbreaks occurred (n=14, halved compared to the previous trial), they usually resolved within 2 weeks, and all but one tail-injured pig were successfully reintroduced back to their home pens after removals. Thus, this study concluded that by employing appropriate enrichment management strategies, tail biting can be kept at a level without a negative impact on the production cost in undocked pigs housed in a fully-slatted system.