J.W. van de Vis

Welfare aspects of live chilling and freezing of farmed eel (Anguilla anguilla L.): neurological and behavioural assessment

Abstract The overall objective of the study was to evaluate a slaughter method of eels, which consisted of chilling until their body temperature was Firstly, 19 eels with an average live weight of 758±44 g were restrained and equipped with EEG, ECG electrodes and a temperature sensor inside the body. Then, they were placed in the ice water. Indices for the induction of unconsciousness and insensibility were the appearance of theta and delta waves and no response on pain stimuli, which disappeared at a body temperature of 8.0±2.1 °C after 12±5 min in 15 eels. The responses to pain stimuli did not disappear in three eels. Within a confidence level of 95%, the percentage of eels that is not effectively stunned during the procedure in ice water of n =14) to 7±4 ( n =11) and became irregular during cooling down. When placed in the brine water of −18 °C, the EEG showed rapid and extreme depolarisation of the membranes, which started after 27±17 s ( n =18). The ECG showed fluttering of the heart in all eels. None of the eels recovered after this procedure. For 10 eels with an average live weight of 128±27 g, it was observed that the body temperature decreased from 17.1±0.6 to 4.0±0.5 °C in the ice water. After 15 min in the brine water of −16.1±2.2 °C, the body temperature decreased to −3.1±2.3 °C. Finally, three groups of seven eels and eight single eels were placed in ice water of −0.0±0.1 °C. The observation of unrestrained eels revealed four phases. Animals were (1) swimming around in the water, (2) attempting to escape from the ice water, (3) pressing their nose to the wall or corner while showing clonic muscle cramps, and finally (4) breathing only, while all other muscle activity was totally suppressed. Afterwards, they were transferred to cold brine at −18 °C, and none of the eels recovered. The eight control eels, which were transferred to water at 18 °C, swam around, except for one that was lying in an S-shape position at the bottom. After 570 and 605 s, two eels tried to escape from the box. The obtained results show that the eels, which were transferred from water at 18 °C to ice water, might be stressed, a specific behaviour and an irregular heart rate were observed. From an animal welfare point of view, it is therefore not recommended to stun eels by live chilling. Moreover, at least 5% of the eels will not be stunned at a body temperature of

The impact of elevated water nitrite concentration on physiology, growth and feed intake of african catfish clarias gariepinus (burchell 1822)

The nitrate threshold concentration in rearing water of African catfish (Clarias gariepinus) was assessed. Female African catfish with an initial mean (SD) weight of 154.3 (7.5) g were exposed to 0.4 (Control), 1.5, 4.2, 9.7 and 27.0 mM nitrate for 42 days. Mean (SD) plasma concentrations of nitrate increased from 71 (29) to 6623 (921) lM at the highest ambient nitrate level. Mean (SD) plasma nitrite concentration ranged from 1.2 (0.5) to 7.9 (9.0) lM. Haematocrit, plasma concentrations of non-esterified fatty acids (NEFA), cortisol, glucose, lactate, osmolality, gill morphology and branchial Na/K-ATPase activity were not affected. Feed intake and specific growth rate were significantly reduced at the highest nitrate concentration. We advise not to exceed a water nitrate concentration of 10 mM (140 mg L 1 NO3-N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.

The effects of environmental enrichment and age-related differences on inhibitory avoidance in zebrafish (Danio rerio Hamilton).

The inhibitory avoidance paradigm allows the study of mechanisms underlying learning and memory formation in zebrafish (Danio rerio Hamilton). For zebrafish, the physiology and behavior associated with this paradigm are as yet poorly understood. We therefore assessed the effects of environmental enrichment and fish age on inhibitory avoidance learning. Fish raised in an environmentally enriched tank showed decreased anxiety-like behavior and increased exploration. Enrichment greatly reduced inhibitory avoidance in 6-month (6M)- and 12-month (12 M)-old fish. Following inhibitory avoidance, telencephalic mRNA levels of proliferating cell nuclear antigen (pcna), neurogenic differentiation (neurod), cocaine- and amphetamine-regulated transcript 4 (cart4), and cannabinoid receptor 1 (cnr1) were lower in enriched-housed fish, while the ratios of mineralocorticoid receptor (nr3c2)/glucocorticoid receptor α [nr3c1(α)] and glucocorticoid receptor β [nr3c1(β)]/glucocorticoid receptor α [nr3c1(α)] were higher. This was observed for 6M-old fish only, not for 24-month (24 M) old fish. Instead, 24 M-old fish showed delayed inhibitory avoidance, no effects of enrichment, and reduced expression of neuroplasticity genes. Overall, our data show strong differences in inhibitory avoidance behavior between zebrafish of different ages and a clear reduction in avoidance behavior following housing under environmental enrichment.

Evaluation of captive needle stunning of farmed eel (Anguilla anguilla L.): suitability for humane slaughter

Abstract In the study, 53 eels with a live weight of 700 to 800 g were restrained and equipped with EEG and ECG electrodes before stunning. The eels were mechanically stunned by a captive needle pistol using a shooting pressure of 8 bar and an air injection of 3 bar during 1.5 s. The behaviour was observed during and after stunning. Indices for the immediate induction of unconsciousness and insensitivity were the appearance of theta and delta waves tending to an iso-electric line, i.e. no brain activity. The duration of these waves averaged 11±8 s ( n =32) on the EEG. Another nine animals showed directly after stunning no brain activity. Due to severe clonic cramps five animals were stunned twice. The ECG showed fluttering of the heart configuration immediately after stunning in all eels. It was concluded that within a confidence level of 95%, taking into account the number of animals with a reliable EEG ( n =42), at least 93% of the eels were effectively stunned by a correctly positioned captive needle pistol. It was easy to stun eels with a captive needle pistol using air pressure; however, more research is needed for the development of a restraining and stunning device suitable for use in practice.

Fish welfare assurance system: initial steps to set up an effective tool to safeguard and monitor farmed fish welfare at a company level

The objective was to take a first step in the development of a process-oriented quality assurance (QA) system for monitoring and safeguarding of fish welfare at a company level. A process-oriented approach is focused on preventing hazards and involves establishment of critical steps in a process that requires careful control. The seven principles of the Hazard Analysis Critical Control Points (HACCP) concept were used as a framework to establish the QA system. HACCP is an internationally agreed approach for management of food safety, which was adapted for the purpose of safeguarding and monitoring the welfare of farmed fish. As the main focus of this QA system is farmed fish welfare assurance at a company level, it was named Fish Welfare Assurance System (FWAS). In this paper we present the initial steps of setting up FWAS for on growing of sea bass (Dicentrarchus labrax), carp (Cyprinus carpio) and European eel (Anguilla anguilla). Four major hazards were selected, which were fish species dependent. Critical Control Points (CCPs) that need to be controlled to minimize or avoid the four hazards are presented. For FWAS, monitoring of CCPs at a farm level is essential. For monitoring purposes, Operational Welfare Indicators (OWIs) are needed to establish whether critical biotic, abiotic, managerial and environmental factors are controlled. For the OWIs we present critical limits/target values. A critical limit is the maximum or minimum value to which a factor must be controlled at a critical control point to prevent, eliminate or reduce a hazard to an acceptable level. For managerial factors target levels are more appropriate than critical limits. Regarding the international trade of farmed fish products, we propose that FWAS needs to be standardized in aquaculture chains. For this standardization a consensus on the concept of fish welfare, methods to assess welfare objectively and knowledge on the needs of farmed fish are required.

Head-to-Cloaca Electrical Stunning of Broilers

This study was performed to identify the electrical current and exposure duration that would instantaneously render broiler chickens unconscious at slaughter when using a head-to-cloaca water bath stunner. The water in which the head was immersed was one electrode, and a steel-coned or cutaneous U-shaped electrode penetrating the cloaca was the other electrode. When an electrode penetrating the cloaca was used, a 640-Hz sinusoidal current induced a tonic-clonic phase on the electroencephalogram that lasted for 10 +/- 3 s and an exhaustion phase that lasted for 34 +/- 12 s. The heart rate was 375 +/- 39 beats/min before stunning. After stunning, the electrocardiogram revealed fibrillating for 429 +/- 58 s, after which the heart activity stopped. When a U-shaped electrode was placed on the skin at the cloaca, the same phenomenon was induced. A general epileptiform insult was induced when using a pulsed alternating square wave current of 33 mA (peak 60 V, 600 Hz, and a duty cycle of 50%), which lasted, on average, for 25 s (n = 25). When the broilers were bled within 14 s after stunning, they remained unconscious and the heart activity stopped after 237 +/- 103 s. We concluded from this experiment that broilers were effectively stunned with an average current of 111 mA (50 V, 640 Hz, sinusoidal alternating current) for 1 s when using a water bath in which the head of the broiler was immersed in water, with the water being one electrode and a steel electrode penetrating the cloaca or placed around it being the other electrode. Energy use could be reduced when an alternating pulsed square wave is used when the broilers are stunned, by using a current of approximately 33 mA (peak of 60 V, frequency of 600 Hz, and a 50% duty cycle).

Stunning and killing of farmed fish: How to put it into pratice?

In this article an approach is presented to implement stunning and killing of farmed fish in practice. First, in a laboratory setting, the conditions need to be established to achieve an effective stun without causing avoidable distress and discomfort. Product quality is evaluated to assess the impact of stunning method on carcass quality. During subsequent implementation in a commercial setting, it is likely that stress-physiological and neurophysiological measurements are not feasible and, therefore, only behavioral and physical measurements can be performed. Finally, stunning and killing of farmed fish in practice should be controlled using a process-oriented quality assurance system.