Assessment of Total Antioxidant Capacity in Serum of Heathy and Stressed Hens

SIMPLE SUMMARY: In living organisms, the antioxidant defense system serves to counteract reactive oxygen (ROS) and nitrogen (RNS) species, thereby protecting cellular targets against their oxidative damage; it includes a combination of different substances of endogenous or exogenous origin. Several methods were developed to assess the overall antioxidant capacity or the precise determination of individual key antioxidants. In the present study, the total antioxidant capacity (TAC) in healthy and dexamethasone-stressed hen serum was measured by applying four different spectrophotometric methods intended for both clinical and research studies, which could be automated on clinical auto-analyzers, thus allowing rapid and not expensive data collections. TAC values assessed by all four methods did not change throughout the experimental period in the control group, whereas significant changes were shown by all adopted assays in the stressed group, with some remarkable differences, probably due to the different contribution in each assay of the various antioxidant substances present in the samples. Therefore, when TAC evaluation is necessary to verify if animals are experiencing oxidative stress (OS) or to evaluate possible benefits from an antioxidant-enriched diet, TAC assessment should involve multiple assays, due to the different analytical technologies on which their assessments are based. ABSTRACT: Total antioxidant capacity (TAC) in healthy and dexamethasone-stressed hens was measured by applying four different spectrophotometric methods—the ferric reducing ability (FRAP) assay, the 2,2′-azino-bis (3-ethylbenzotiazoline-6-sulphonic acid) (ABTS) radical cation decolorization assay, the free radical scavenging activity (FRSA), and the total thiol levels (TTL). TAC assessed by all four methods did not change throughout the experimental period in the control group, whereas significant changes were shown by all adopted assays in the stressed group with some remarkable differences. TAC increased in the stressed group when FRAP and ABTS assays were applied, while it was reduced when sera were assessed by FRSA and TTL assays. Furthermore, FRAP assay was the only test able to show a significant change in TAC immediately after the end of the induced stress. At the end of the experimental period, TAC assessed by ABTS and FRSA assays showed a complete recovery in the stressed group, whereas TAC assessed by FRAP and TTL assays still showed significant persistent differences when compared to the control group. The observed differences in TAC are discussed in the light of the different contribution in each assay of the various antioxidant substances present in the samples.