Different frequency for electronarcosis in preslaughter stunning of cobia (Rachycentron canadum)

There are no legal guidelines for the eletronarcosis of fsh in Brazil, and no recommendations on the parameters (voltage (Hz), current (A), time) to be used in pre-slaughter stunning of these animals. The aim of this study was to establish better parameters of eletronarcosis and to evaluate the infuence of this pre-slaughter stunning, on the welfare and meat quality during 21 days ice storage in cobia (Rachycentron canadum). Four stunning methods were evaluated: 1) Hypothermia (ice and water solution 1:1), 2) Eletronarcosis with 800Hz, 1.7 A per three seconds, 3) (Eletro 800) Eletronarcosis with1200 Hz, 2.5 A per three seconds (Eletro 1200) and 4) Anesthesia with eugenol. We used a n = 12 fshes per treatment. After stunning fsh were slaughtered by bleeding through the gill cut and kept in thermal boxes with ice for 21 days. Were evaluated rigor mortis index, muscle pH, dielectric properties, volatile nitrogen bases (VNB) in selected time periods after slaughter. For comparisons between treatments, we used one-way analysis of variance (ANOVA) for parametric data and Kruskal-Wallis test for non-parametric data (P<0.05). Fishes stunned by hypothermia and anesthesia took respectively 10.54 and 13.14 minutes to show refexes indicative of insensitivity, while the eletronarcose promoted the same condition in 3 seconds. The rigor mortis onset was observed at 24 hours after slaughter for fsh stunned by all treatments, except for the Electro 1200, in which this phenomenon occurred at 120h of storage. Fish stunned by anesthesia, Eletro 1200 and Electro 800 showed statistically equal pH means, lower than those stunned by Hypothermia (6.57, 6.58, 6.63 and 6.84 respectively). For the dielectric properties of the meat, the Electro 800 treatment presented the highest mean (6.9); the treatments Hypothermia and Anesthesia promoted intermediate values (6.2 and 5.3), while Eletro 1200 presented the lowest mean (2.6). VNB values difered signifcantly between groups (P <0.01).The highest values were observed in fsh stunned by hypothermia while the lowest value were in fsh stunned by Eletro 1200. Eletronarcosis with1200 Hz, 2.5 A per 3 seconds is able to promote fast apparent stunning in cobia, respecting the concepts of animal welfare and humane slaughter. In addition, this treatment provided greater stability of cobia meat kept on ice.