Electroencephalographic spectrum power of sheep's brain after stunning

Electroencephalogram (EEG) assessment of brain activity before and after electrical stunning in the Nile crocodile (Crocodylus niloticus)

Electrical stunning is used to capture crocodiles to perform routine management procedures. It is essential from a welfare point that electrical stunning must cause unconsciousness in animals. However, there is no information of whether or not electrical stunning causes unconsciousness in the Nile crocodile (Crocodylus niloticus). The purpose of the study was to assess brain activity before and after electrical stunning in crocodiles using a 5-channel referential electroencephalogram analysis to determine consciousness. Behavioural indicators and electroencephalogram recordings of 15 captive-bred crocodiles were captured and analysed using power spectral density analysis immediately before and after stunning and then at 60 s intervals until 5 min post-stunning. A standardised stun of 170 Volts was applied for 5-7 s on the wetted neck. Unconsciousness was defined as a decrease in alpha wave power and increase in delta wave power. Three of the electroencephalograms could not be assessed. Unconsciousness was identified in 6 out of 12 crocodiles and lasted for an average for 120 s. An increase in electroencephalogram waveform amplitude and tonic-clonic seizure-like waveform activity and behaviour indicators were not reliable indicators of unconsciousness. Further research should be focused on improving the efficiency and reliability of electrical stunning.

Evaluation of a commercial electrical stunning method for farmed grower saltwater crocodiles (Crocodylus porosus) using non-invasive EEG measurements

The aim of this study was to assess welfare outcomes of electrical stunning as a means of restraint in farmed grower saltwater crocodiles (Crocodylus porosus). Physical handling of a stunned, unconscious crocodile is far safer for the operator than handling a fully conscious animal. Electroencephalogram (EEG) was recorded before and after the application of electrical stunning at 50 Hz or 400 Hz using an electrical stunner applied to the cranial plate (Position 1: P1-50 Hz; n = 31, P1-400 Hz; n = 29) or immediately behind the skull (Position 2: P2-50 Hz; n = 29; P2-400 Hz; n = 30). For all electrical stuns, percentage total EEG power in a 10-s epoch decreased in the alpha and beta frequency bands; and increased in the delta and lower frequencies bands. All electrical stuns resulted in increased strength of signal, based on the quadratic mean EEG power in all frequency bands of the EEG. Greatest change in power occurred in the delta frequency band, with P1-50 Hz. This was greater than with P2-50 Hz; while decibel change using 400 Hz at either position was intermediate and not significantly different from either. Application of either electrical stunner at position 1 resulted in seizure-like activity and activation in low frequencies, but at position 2 this was not consistent across all animals. The ability of the electrical stunning equipment to consistently induce recoverable unconsciousness could be ranked in decreasing order as: P1-50 Hz > P1-400 Hz = P2-50 Hz > P2-400 Hz. Based on behavioural observations, all animals in the study appeared to stunned however evaluation of duration of EEG changes indicates that use of the electrical stunning equipment at 50 Hz would allow some margin for inaccuracies in tong placement, while achieving a consistently reliable stun.

Application of Electroencephalography in Preslaughter Management: A Review

Electroencephalography (EEG) can be reliable for assessing the brain’s electrical activity of preslaughter stress and pain. The duration between the ventral neck cut and induction of a state of unconsciousness/insensibility is crucial in the slaughtering of animals, reducing pain, fear, and distress. Various EEG variables, such as median frequency (F50), the total power of EEG spectrum (Ptot), waves patterns (amplitude and frequencies), epileptiform EEG, index of consciousness, and isoelectric EEG, are used to identify a valid indicator of the state of unconsciousness. Association among various behavioral, physiological, and hematological parameters with EEG variables could provide an overall assessment and deep insights into the animal stress levels or welfare status during various managemental and preslaughter operations, such as transport, stunning, and slaughtering operations. The application of EEG could help in further refining the stunning technologies and slaughter protocols in livestock, poultry, and fish. The present review analyzed the application of EEG as a neurophysiological tool for assessing animal welfare during the critical state of preslaughter handling and slaughter, thus ensuring proper compliance with animal welfare principles.

Welfare of sheep and goats at slaughter

The killing of sheep and goats for human consumption (slaughtering) can take place in a slaughterhouse or on-farm. The processes of slaughtering that were assessed for welfare, from the arrival of sheep and goats until their death (including slaughtering without stunning), were grouped into three main phases: pre-stunning (including arrival, unloading from the truck, lairage, handling and moving of sheep and goats); stunning (including restraint); and bleeding. Stunning methods were grouped into two categories: mechanical and electrical. Twelve welfare consequences that sheep and goats may experience during slaughter were identified: heat stress, cold stress, fatigue, prolonged thirst, prolonged hunger, impeded movement, restriction of movements, resting problems, social stress, pain, fear and distress. These welfare consequences and their relevant animal-based measures are described in detail in this Scientific Opinion. In total, 40 welfare hazards that could occur during slaughter were identified and characterised, most of them related to stunning and bleeding. Staff were identified as the origin of 39 hazards, which were attributed to the lack of appropriate skill sets needed to perform tasks or to fatigue. Measures to prevent and correct hazards were identified, and structural and managerial measures were identified as those with a crucial role in prevention. Outcome tables linking hazards, welfare consequences, animal-based measures, origin of hazards and preventive and corrective measures were developed for each process. Mitigation measures to minimise welfare consequences are proposed.

Electroencephalographic and blood parameters changes in anaesthetised goats subjected to slaughter without stunning and slaughter following different electrical stunning methods

Electrical stunning is the most widely used stunning method for sheep and goats. Because low frequency head-to-back electrical stunning induces cardiac arrest, it is non-compliant with halal requirements. In addition, conventional head-only electrical stunning method can have adverse effects on carcass and meat quality. To address these issues high-frequency electrical stunning systems were developed. High frequency head-to-back removes the potential for pain and distress compared with non-stunned slaughter and does not induce cardiac arrest like low frequency head-to-back stunning making it appropriate for halal. However, this claim is yet to be proven through a comprehensive neurophysiological study. Thus, the present study examined the effects of different pre-slaughter electrical stunning methods and slaughter without stunning on electroencephalographic and blood biochemistry changes. Thirty-two male Boer crossbred bucks were distributed into four groups of eight animals each and subjected to slaughter without stunning (SWS), low frequency head-only (LFHO) and low frequency head-to-back (LFHB) or high frequency head-to-back electrical stunning (HFHB). Slaughtering of animals with or without stunning was performed under minimal anaesthesia. Based on electroencephalograph results, at slaughter, the SWS animals showed an increase in brain electrical activity, which is consistent with the presence of post slaughter noxious sensory input associated with tissue damage. Meanwhile the electroencephalograph activities decreased immediately after application of electrical stunning in all animals, suggesting that they were insensible to pain during and after the neck cut. Electrical brain activities for goats subjected to HFHB were comparable to those for LFHO and those for LFHB. The percentage of animals that exhibited severe clonic activity was significantly lower after LFHB or HFHB stunning compared with LFHO. The concentrations of catecholamines and hyperglycemia in electrically stunned goats were higher compared with those from SWS. It was observed that LFHB caused cardiac arrest in all goats whereas all HFHB goats had no cardiac arrest. High frequency head-to-back electrical stunning may be an improvement on non-stunned slaughter and has advantages for meat quality. However, stunning effectiveness after head-to-back electrical stunning with high frequencies needs to be evaluated under industrial conditions before any recommendation is given.