Effects of oregano essential oil or quercetin supplementation on body weight loss, carcass characteristics, meat quality and antioxidant status in finishing pigs under transport stress

• Oregano essential oil may favourably affect growth traits of finishing pigs.
• Oregano essential oil may improve carcass quality in transported pigs.
• Oregano essential oil and quercetin may lower oxidative stress in transported pigs.

This study compared the effects of dietary oregano essential oil (OEO), quercetin or vitamin E (vit E), on the live body weight loss, carcass characteristics, meat quality and antioxidant status of pigs after transportation. A total of 340 finishing pigs (Large White×Landrace) with an initial body weight of 74 kg (±4.0 kg) were randomly assigned to one of four treatment groups (five replicate pens per treatment, 17 pigs per pen). Pigs consumed the basal diet (control) or the basal diet supplemented with 200 mg vit E/kg (positive control), 25 mg OEO/kg or 25 mg quercetin/kg for 4 weeks. After this period, 144 pigs (36 pigs per treatment) were transported for 5 h before slaughter. Compared with the control group, the OEO or quercetin groups had a higher average daily gain (P<0.05), and the OEO group also had a lower feed intake/gain (P<0.05). The live body weight loss was less in the OEO group after 5 h transportation (P<0.05) than in the control group. The hot carcass weight and dressing percentage were higher in the OEO group after 5 h of transportation (P<0.05) than in the control group. After slaughter, the pH value at 45-min postmortem and Opto-star value (meat color) at 24-h postmortem increased in the vit E, OEO or quercetin groups (P<0.05) compared with the control group. The vit E or quercetin groups also exhibited higher 24-h postmortem pH values (P<0.05) than the control group. The Longissimus thoracis et lumborum muscle of pigs from the OEO or quercetin groups produced lower 24-h drip loss values (P<0.05) than that of pigs from the control group. Compared with the control group, the OEO or quercetin groups had reduced levels of TBARS (thiobarbituric acid reactive substances) and ROS (reactive oxygen species) in serum, muscle and liver (P<0.05), while the vit E group had reduced levels in serum only (P<0.05). The OEO or quercetin groups also had increased levels of Gpx (glutathione peroxidase) and T-SOD (total superoxide dismutase) activity in serum and liver compared with the control group (P<0.05). Conversely, there were no differences between the vit E and control groups in Gpx or T-SOD activities. In conclusion, supplementation with dietary OEO or quercetin may be superior to supplementation with dietary vit E in alleviating the negative effects of transportation on pigs by improving the pigs’ antioxidant status.