Evaluating loose materials and space allowance to improve welfare in commercial weaner and finisher pigs.

Abstract

The welfare of commercial pigs, especially concerning the reduction of tail biting, is an ongoing topical issue in current farming systems. Inadequate space allowance and lack of suitable loose material have been identified as two of the main risk factors for tail biting in pigs. This study evaluated the effectiveness of four manipulable loose materials (Straw, Haylage, Hay, and Grass) in reducing tail biting in pigs reared in pens containing either 8, 10, or 12 pigs (weaner: 0.62, 0.49, 0.41 m²/pig; finisher: 1.24, 1.00, 0.83 m²/pig, respectively). Although the study design conflates stocking density, space allowance, and feeder space, making it impossible to evaluate each factor independently, this confound allows for on-farm application. At weaning (approx. 4 weeks), forty-seven litters with undocked tails were assigned as litter groups to enrichment and stocking density treatments using a 4 × 3 experimental design. The fully slatted pens were equipped with single-space feeders. Manipulable materials were provided ad lib via a mesh rack hung on the front wall of the pen. Pens were observed twice daily for any indication of tail biting. Lesion scoring at the individual pig level was performed weekly. Pig behaviour was observed at the group level directly every fortnight, and by video on four occasions (1, 6, 10, and 18 weeks postweaning). Weights were taken one day prior to weaning, 63 days postweaning, and at 22 weeks of age, at which time pigs were slaughtered. Carcass characteristics were obtained from the slaughterhouse. Greater space per pig benefited welfare, as indicated by physical and behavioural measurements. Pigs stocked in groups of 8 and 10 displayed significantly less aggressive and damaging behaviour, fewer and more manageable tail biting outbreaks, and had more undamaged tails than pigs in groups of 12. In addition, pigs in lower-stocked pens were heavier at the end of their lives, creating potential to sell pigs earlier. Interestingly, the type of loose material had no significant impact on most measures, but pigs provided with grass engaged significantly more with the rack than those with other loose materials, and had fewer, more manageable tail biting outbreaks. This study contributes to existing research that suggests the current European Union legal minimum requirement for space allowance should be increased to improve pig welfare, reduce damaging behaviour, and tail biting outbreaks in pigs, especially with undocked tails.