Effect Of Oregano Essential Oil On Reducing Transport Stress And Improving Meat Quality In Pigs

Transportation stress can result in significant economic losses to producer due to decreased animal productivity and increased mortality in pig production. Not only the levels of stress hormone, physiological and biochemical of tissue and organ, antioxidation and intestinal function were changed, but also pH, drip loss and colour of meat were changed in transportation stress situation. Thus, we speculate that the changes of these indexes and functions existed inevitable connection and affected meat quality. Plant extracts of oregano essential oils has so many functions such as antioxidant, antibacterial and improving the function of intestinal. All of these can affect the metabolism of the body. In addition, oregano essential oils (OEO)also has to improve meat quality and prolong the shelf life of the meat. The purpose of this study was to determine the effect of oregano on improve meat quality in transportation stress.This study mainly includes three parts. Firstly, the current study was to built a model of transportation stress and to evaluate feasibility of this model used in the study of energy metabolism and morphology of muscle in rats; Secondly, using this model, to research the effect and mechanism of oregano essential oils on muscle damage under transportation stress; Thirdly, to assess the potential of oregano essential oils as a dietary supplement for finishing pigs to alleviate transport stress. Also to evaluate the effects of dietary oregano essential oils on growth performance, meat quality and muscle Hsps expression after transport stress in finishing pigs.1 The feasibility of the model of transportation stress used in the study of muscle damage in ratsSix-week-old healthy male SD rats were placed in 35℃ shaker (60r/min,2 h) to induce transportation stress. Compared with the control group, the levels of cortisol, norepinephrine and CRF in serum was extremelysignificantly increased in the stress control group (P< 0.01), the content of malondialdehyde (MDA) in serum was extremely increased (P< 0.01). At the same time, the content of MDA in muscle was significantly increased (P<0.01), the activity of GSH-Px was extremely significantly decreased (P< 0.01), the activity of CAT was significantly reduced (P<0.05). The content of ROS in the muscle was extremely increased (P<0.01). Muscle fiber have been broken on muscle morphology, these phenomenon indicated that muscle has already damaged. These results showed that the model can be used to study the influencing factors of muscle damage.2 The effect and mechanism of oregano essential oilson muscle energy metabolism and morphology in transportation stressBy using the model of transportation stress, and adopt double factor experiment design.Six-week-old healthy male SD rats were randomly allotted to 4 treatments arrangement and 9 replicates with 1 rat per group.Each group was randomly allocated to 1 of 4treat containing no stress, stress, no stress with OEO (orally 5mg/t.bw) and stress with OEO (orally 5mg/t.bw). The stress hormone physiological and biochemical indicators, antioxidant, muscle morphological and intestinal immunity index were determinated. The results showed that the oregano essential oils didn’t significantly improve daily gain of rats, but can significantly reduce feed conversion ratio (P<0.05). Compared with the negative control group, experimental group can significantly reduce the levels of cortisol and CRF in serum (P< 0.05) after stress; at the same time very significantly reduced the level of LDH in serum of rats (P< 0.01). The content of ROS was significantly reduced in the experimental group (P< 0.05). The activity of SOD and GSH-Px in serum were extremely significantly increased (P< 0.01) in the experimental group. Compared with the negative control group, the activity of SOD were significantly increased on 0 h and 48 h after slaughter in the muscle (P< 0.05), the content of MDA (P< 0.01) and lactic acid (P< 0.05) were significantly reduced after slaughter in the muscle. The content of glycogen was extremely significantly increased (P< 0.01) in the experimental group. The activity of SOD and GSH-Px were significantly increased in the intestinal feed oregano under stress.The content of MDA were significantly reduced in the intestinal (P< 0.05). The level of TNF-a and IL-6 were significantly reduced (P< 0.05). These results showed that OEO can improve antioxidant capacity of intestinal and reduce the production of inflammatory cytokines. These results showed that reduced the levels of glucocorticoid and regulate the metabolism of muscle energy, and then reduce anaerobic glycolysis and the production of lactic acid, prevent of pH falling fast. And OEO can increase the activity of antioxidant enzymes and reduce the generation of free radicals in the body. Furthermore, OEO can reduce the damage of muscle because of its antioxidant ability.3 Effect of dietary oregano essential oils supplementation on growth performance and meat qualityA total of two hundred and eighty-eight pigs (Landrace×Yorkshire) were randomly allotted to 3 treatments arrangement based on initial body weight (initial body weight BW=77.80±5kg) and 6 replicates with 16 pigs per pen in each replication. Each group was randomly allocated to 1 of 3 finishing diets containing commercial basal diets (the control),200 mg/kg VE, or 25 mg/kg OEO of feed. After 28-d feeding trial,60 pigs from each group were subjected either to no stress (NS) (low stocking density and rest for 20 h) or 5h of transportation stress (TS). OEO supplementation increased the average daily gain (ADG), and significantly decreased the feed conversion ratio (FCR) (P< 0.05). Serum cortisol concentrations were greatly reduced (P=0.01) in pigs fed VE and OEO diet (transportation stress×diet interaction, P<0.01). ROS levels were significantly increased in the serum (P<0.01) and liver (P=0.01) of TS pigs. Similarly, MDA levels were observably elevated in the serum (P=0.05) and liver (P=0.05) of TS pigs. The SOD activity was slightly increased (P=0.08) and GSH-Px was markedly higher (P=0.01) in pigs fed VE and OEO diet than the control diet in the serum. The SOD activity was dramatically raised no matter transportation (P< 0.01) or dietary treatment (P=0.01), and T-AOC activity was significantly higher (P< 0.01) after transportation than no stress in liver. Muscle MDA, SOD, and GSH-Px levels were significantly increased after 5-h transportation in TS pigs (P< 0.05).However, dietary supplementation with OEO significantly decreased the muscle MDA level (P=0.04), particularly in TS pigs fed OEO than in TS pigs fed the control diet (transport×diet; P=0.04).TS pigs had lowerlongissimus thoracis45 min pH (pHi) and higher longissimus lumborum (LL) drip loss than NS pigs. Notably, dietary OEO supplementationsignificantly decreased LL drip loss under transport stress.The levels of HSP27 and HSP90 mRNA were significantly increased (P<0.01) after transportation compared with the control pigs.Histological analysis revealed intestinal epithelial damage in TS pigs. VE and OEO supplementation increased VH (P<0.01), VCR (P=0.01) and VSA(P=0.03).To sum up, the conclusions of this study was to:(1) The model of transportation stress rats was established. Related parameters for temperature 35℃,the speed of shaking table for 60 r/min, Swing duration for 2 h.(2) Oregano essential oils regulated muscle damage through three aspects:Oregano essential oils lead to reduce the levels of glucocorticoid and regulate the metabolism of muscle energy, and then reduce anaerobic glycolysis and the production of lactic acid, to prevent of pH falling fast; oregano essential oils can increase the activity of antioxidant enzymes and reduce damage of free radicals in the muscle; oregano essential oils can prevent muscle cell membrane lipid oxidation,by reducing the generation of MDA.(3) OEO may exert growth-promoting effects on finishing pigs during heat stress condition. OEO supplementation might be able to alleviate transportation stress andreduce lipid oxidation. Importantly, it is found that dietary supplementation with OEO decreased meat drip loss under transport stress, which may be due to its role in protecting pigs from oxidation stress and thus reducing lipid oxidation during road transportation. These results indicated that supplementation with 25 mg/kg OEO of feed 4 weeks before being transported to the market are beneficial in alleviating TS and in improving antioxidative activity and meat quality. Moreover,25 mg/kg OEO had similar effects as 200 mg/kg VE or even better.