Effects of dietary oregano essential oil supplementation on the stress response, antioxidative capacity, and HSPs mRNA expression of transported pigs

• OEO may alleviate transportation stress.
• OEO may enhance antioxidative capacity.
• OEO is similar to VE during transportation stress of pigs.

Transportation stress affects carcass quality, metabolism and immune function. The utilization of feed additives is a possible strategy of mitigating physical and psychological stresses after animal transportation. Oregano essential oil (OEO) is an aromatic plant extract that mainly contains carvacrol and thymol. However, the effects of dietary supplementation with OEO for the welfare of transported pigs are limited. This study aimed to investigate the effect of OEO on alleviating stress and increasing antioxidative capacity after the transportation of finishing pigs. 180 crossbred pigs were randomly allocated to 1 of 3 diets: the basal diets, 200 mg kg−1 vitamin E (VE), or 25 mg kg−1 OEO. Each group was divided into two subgroups: no stress (NS) or transportation stress (TS) after 28 days. Here we report that serum cortisol and norepinephrine concentrations of transported pigs were significantly reduced (P<0.05) in OEO diet. Reactive oxygen species (ROS) and malondialdehvde (MDA) were significantly increased in the serum (P<0.05) and liver (P<0.05) of TS pigs. Serum glutathione peroxidase (GSH-Px) was markedly raised (P=0.01) in dietary treatment. Liver SOD was dramatically raised no matter transportation (P<0.01) or dietary treatment (P=0.01). Liver heat shock protein (HSP) 27 and HSP90 were significantly increased (P<0.01) after transportation. These results indicated that OEO is beneficial in alleviating transportation stress and improving antioxidative activity, similar to VE.