Effect Of Dietary Supplementation With Carnosine And Vitamin E On Antioxidant Capacity And Meat Quality Of Finishing PIGS

The study was conducted to investigate the supplemental effect of camosine, vitamin E and combination of both on antioxidant capacities and meat quality of pigs during the final finishing phase. By measuring carcass quality, meat quality, antioxidant levels, mRNA levels and protein levels of critical factors in NF-E2-related Factor2(Nrf2) pathway, to explore the antioxidant mechanism of how camosine and vitamin E affect the meat quality, the results of this study could provide a theoretical basis for ante-mortem nutritional regulation technology to improve pork quality.1. Effect of camosine and vitamin E on carcass quality and meat quality of finishing pigs. Sixty well grew Duroc×Yorkshire×Landrace finishing pigs were selected, and the average weight was75kg.2×2factorial experimental design was used, four experimental diets formulated as two levels of added vitamin E (0and400mg/kg a-tocopheryl acetate of feed) and two supplemental levels of camosine (0and150mg/kg camosine of diet). The test period was28d. Each group had3replicates (with5pigs per replicate), so each treatment had15pigs in total. Six pigs in each treatment (with2pigs per replicate) were randomly selected and slaughtered at the end of the trial. The results showed that:Dietary incorporations of camosine or vitamin E exerted no effects on carcass characteristics, which included backfat thickness, lean meat percentage and longissimus muscle area, and pH values (P>0.05), but supplementation of vitamin E had a trend to increase pH45min(P=0.1). As for the meat color, supplementation of camosine (P<0.01) and vitamin E (P=0.01) had significantly higher a*value than the control group, and their interaction effects occured (P<0.01), while the L*value and b*values were not significantly affected (P>0.05), but dietary vitamin E had a reduced trend towards the L*value (P=0.1). Supplementation of carnosine and vitamin E showed no significant effect on other meat quality including drip loss, cooking loss and shear force, and textural characteristics including hardness, cohesiveness, elasticity, adhesion and chewing traits, and longissimus muscle nutrients composition including moisture, crude fat, crude ash and crude protein, and contents of inosine monophosphate (P>0.05).2. Effect of dietary carnosine and vitamin E on the antioxidant enzyme activity and expression of critical factors on Nrf2signaling pathway in finishing pigs. The test results showed:dietary vitamin E supplementation significantly increased a-tocopherol concentrations in serum (P=0.02), liver (P<0.01) and longissimus muscle (P<0.01), while dietary carnosine had no influence on a-tocopherol concentrations (P>0.05), and camosine and vitamin E had no interaction effect on α-tocopherol concentrations (P>0.05). Dietary vitamin E significantly reduced malondialdehyde (MDA) concentrations in liver and longissimus muscle (P<0.01), while serum MDA was not significantly affected (P>0.05), carnosine had no significant effect on MDA in these three tissues (P>0.05). Dietary carnosine and vitamin E had no significant effects on glutathione peroxidase (GSH-PX), catalase (CAT) and superoxide dismutase (SOD) activities (P>0.05), while dietary vitamin E had an increasing trend on CAT activity of longissimus muscle (P=0.06) and significantly increased total antioxidant capacity (TAOC) in liver and longissimus muscle (P<0.01), while dietary camosine only showed an increasing trend on TAOC in liver and longissimus muscle (P=0.10and P=0.07), and there was no interaction effect (P>0.05). Dietary carnosine and vitamin E had no significant effects on SOD, glutamate cysteine ligase catalytic subunit (GCLC), Nrf2, heme oxygenase-1(HO1) and NAD(P)H quinine oxidoreductasel (NQO1) mRNA levels in liver and longissimus muscle (P>0.05). In terms of protein expression, protein expression levels of GSH-PX, GCLC and Nrf2in liver and longissimus muscle in control group were the lowest, dietary carnosine group had the highest protein expression in all analysised proteins besides the total Nrf2protein in liver, which dietary combition of carnosine and vitamin E group was the highest. In summary, dietary supplementation of camosine and vitamin E had improvement on the pork quality. Diets supplemented with vitamin E increased the deposition of a-tocopherol in tissues, reduced malondialdehyde contents, and increased the total antioxidant capacity, which showed the deposition of vitamin E in tissues was the basis of its effect on meat quality, while diets supplemented with camosine showed an increased trend on total oxidant capacity. Diets supplemented with camosine and vitamin E did not show a significant effect on mRNA expression of key factors in the Nrf2pathway, while the diet adding carnosine and vitamin E increased the protein expression of key factors in the Nrf2pathway at a certain degree.