Effect of dietary Passiflora incarnata on performance and cortisol levels in postweaning piglets reared with intact tail

Weaning is the most critical phase in pig farming, characterized by efforts to ensure health, performance and welfare of animals. Despite European Directive 2008/120 prohibits the practice of tail docking, it is still widely applied in intensive farming to avoid tail biting. The aim of the study was to evaluate the effect of a nutritional strategy based on the supplementation of the calming and anti-inflammatory extract of Passiflora incarnata on growth performance and physiological indicators in postweaning piglets reared with intact tails. A total of 120 piglets (average body weight: 9.07 ± 0.21 kg) were assigned to two dietary treatments: control diet (CON) and CON supplemented with 1 kg/t of P. incarnata (PASS). Individual piglets’ weight and pen feed consumption were recorded at day (d) 0 and d-28, and the average daily gain (ADG) and feed conversion ratio (FCR) were calculated. Cortisol was measured (ELISA test) on saliva samples at d-1 and weekly (d-8, d-15, d-23). Performance data were analyzed by ANOVA with dietary treatment as main effect. Cortisol changes over time were assessed by Friedman test, and Mann-Whitney U test was used to assess dietary treatment effect (significant when P < 0.05 and trend when P < 0.1). No significant difference between PASS and CON was observed for final body weight (22.49 vs 22.50 kg; P = 0.989) and FCR (2.46 vs 2.48; P = 0.856). Salivary cortisol values ranged from 2.3 to 5.4 ng/ml. A significant difference (P = 0.008) between the two experimental groups (5.14 ± 0.65 ng/ml CON vs 2.38 ± 0.67 ng/ml PASS) was observed at d-23 and time showed a tendentially significant effect (P = 0.055). The unchanged growth performance and the lower level of cortisol suggest the usefulness of P. incarnata extract, even if tails lesions and other physiological indicators should be considered.