Validation of a whole-body cortisol extraction procedure for channel catfish (Ictalurus punctatus) fry

Abstract

We validated a whole-body cortisol extraction technique for channel catfish, Ictalurus punctatus, fry. Three volume enhancement methods were tested: CAL method (zero calibrator A diluent added to lipid extract), PBS method (phosphate buffered saline added to lipid extract), and VO method (food grade vegetable oil added to lipid extract). The volume enhancement extracts were evaluated using a commercial radioimmunoassay kit. Sensitivity, accuracy, precision, reproducibility, and parallelism could not be determined for the PBS method as cortisol levels were not detected in any of the extracted samples. Intra-assay coefficient of variation (CV) for the CAL and VO methods were 7.3 and 8.3%, respectively, while inter-assay CV were 9.6 and 10.6%, respectively. Based on the sensitivity, accuracy, precision, reproducibility, and parallelism results, we conclude that the CAL method is the most appropriate method for volume enhancement of catfish fry lipid extract. Using the CAL method to detect cortisol in catfish fry, fish were stressed daily for 2 weeks. Fry weights were similar throughout the study while whole-body cortisol levels were higher (P < 0.01) in stressed fish after 1 day of stress. These data show the CAL method can effectively measure whole-body cortisol in catfish fry.

Effects of release procedures on the primary stress response and post‐release survival and growth of hatchery‐reared spotted seatrout Cynoscion nebulosus

“…Owing to the intermediate size range of C. nebulosus released in this study (50–100 mm) and the rapid pace of the release procedures, venipuncture was not a feasible method for monitoring cortisol as a measure of the effects of hatchery and release procedures. Moreover, whole‐body homogenization and subsequent cortisol extraction (Ramsay et al ., ; Sink et al ., ; Peterson & Booth, ; Yeh et al ., ) developed for quantifying cortisol in small fishes (200–750 mg) was not feasible, as the size of the C. nebulosus in this study was too large for efficient whole‐body homogenization and precise cortisol quantification using that method. This study therefore used an alternative method for cortisol quantification as described and validated by Guest et al .…”

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“…At the each sampling time, three fish per replicate were sampled (nine fish treatment -1 ). Due to inadequate blood volume to accurately measure plasma biochemical parameters in small fish, whole body extracts were used in this study, in previous studies have also used the whole body extracts to measure blood biochemical factors (Ramsay et al, 2006;Prodocimo et al, 2007;Peterson and Booth, 2010). Fingerlings were removed from the tanks and to euthanasia were located immediately in the solution of Clove.…”

Current State of Bacteria Pathogenicity and their Relationship with Host and Environment in Tilapia Oreochromis niloticus

“…In fish, stress is affected by levels of cortisol in combination with behavioral responses [101]. Cortisol redistributes immune system cells, as well as elements of the innate immune system, thus providing the first line of defense in a host [101,102].…”