Ocimum americanum and Lippia alba essential oils as anaesthetics for Nile tilapia: Induction, recovery of apparent unconsciousness and sensory analysis of fillets

Unconsciousness assessment through electroencephalography (EEG), in the process of stunning, for electronarcosis, percussion and anaesthesia for humane slaughter of Nile tilapia

“…Fish submitted to PE, OA or LA met more than four of the criteria studied to consider the fish unconscious. A key point in the spectral analysis is to obtain good quality records with no interference from breathing or cardiac activity, but this issue was not previously reported in earlier studies (BOWMAN; HJELMSTEDT; GRÄNS, 2019;HERNANDEZ et al, 2019;and SANDERCOCK et al, 2014). BOWMAN et al (2019) carried out a spectral analysis in rainbow trout (Oncorhynchus mykiss) submitted to anaesthesia with MS 222 and found no significant differences in the values for F50, low delta and theta frequencies and high alpha and beta frequencies during the evaluation time, as compared to non-anesthetized fish.…”

“…The EEG recordings were filtered using a band pass filter (0.1 to 45 Hz), and the spectral analysis carried out using the following configurations (FFT size: 1K 1024; Data window: Hamming; Overlap: 50%, considering zero frequency) in 2 s epochs (MCKEEGAN et al, 2011(MCKEEGAN et al, , 2013. Using the Labchart, as from the power spectrum, one can calculate the values for total power (Ptot), median power frequency (F50), spectral edge frequency (F95), and the contribution of each frequency to the power spectrum: delta (0-4 Hz), theta (4-8 Hz), alpha (8-12 Hz) and beta (12-32 Hz) of each 2 s (GERRITZEN et al, 2006;HERNANDEZ et al, 2019;SANDERCOCK et al, 2014). In all, 276 epochs were analyzed in FE, 276 OA, 272 LA, 563 HP and 267 SP.…”

“…In all, 276 epochs were analyzed in FE, 276 OA, 272 LA, 563 HP and 267 SP. Seven criteria were considered for the spectral analysis in the minute by minute comparison of the recording with the baseline, in order to consider the fish unconscious: GERRITZEN, 2013;SANDERCOCK et al, 2014), lambs (VELARDE et al, 2002, cattle (GIBSON et al, 2009) and fish (BOWMAN;HJELMSTEDT;GRÄNS, 2019;. However, these studies did not evaluate all the criteria cited above as used in the present study.…”

“…Recently, concern about fish welfare has been increasing in Western countries and a study with 2147 Norwegians showed that they are concerned about fish welfare (Ellingsen et al, 2015). A Latin American study showed that people recognize suffering in common practices using fish for hook and line fishing or in fish-and-pay ponds amongst others, and regarding slaughter, 76.0% and 72% of participants from Bogota, Colombia and Curitiba, Brazil, believed, respectively, that fish should be included in humane slaughter regulations (Rucinque et al, 2017). Public concern encourages new regulations that guarantee fish welfare in all steps of production, mainly at slaughter.…”

“…F50 is more sensitive to changes in lower frequencies, whereas SEF is more sensitive to shifts towards higher frequencies (TONNER; BEIN, 2006). It is well recognized that increases in the EEG Ptot and associated decreases in both F50 and SEF, are correlated with clinical signs of the loss of consciousness and anaesthesia (MARTÍN-CANCHO et al, 2006;MCKEEGAN et al, 2013;SANDERCOCK et al, 2014). The EEG frequencies can be divided into delta (0-4 Hz), theta (4-8 Hz), alpha (8-12 Hz) and beta (12-32 Hz) and increases in the delta and theta frequencies are related to the state of unconsciousness (GERRITZEN et al, 2006).…”