Slaughter Method Research Articles

Efeitos dos métodos de abate e sexo na composição centesimal, perfil de ácidos graxos e colesterol da carne de capivaras

O objetivo desse trabalho foi avaliar os efeitos de metodos de abate (MA) (humanitario (MH) e por tiro (MT)) e sexo na composicao centesimal, perfil de acidos graxos (AG) e colesterol da carne de capivara (Hydrochaeris hydrochaeris L. 1766). Foram abatidos 20 animais (13 machos (M) e 7 femeas (F)) com peso medio de 45,71kg. No musculo longissimus dorsi (LD) foram determinados: umidade, lipidios totais (LT), proteina e cinzas e no semimembranosus (SM), o colesterol por colorimetria e o perfil de AG por cromatografia gasosa. O LD apresentou: 75,87% de umidade, 1,37% de LT, 22,11% de proteinas e 1,09% de cinzas. Houve diferenca (p<0,01) nos teores de LT de M (1,75%) e F (0,98%). Os fatores sexo e MA nao influenciaram: umidade, proteina e cinzas. Os AG encontrados em maior proporcao (%) foram: C16:0 (29,57); C18:1w9 (27,87); C18:2w6 (19,19); C18:0 (6,57); C18:3w3 (4,97); C14:0 (3,64); C20:4w6 (3,45); C18:1w7 (3,31) e C16:1w7 (1,90). A relacao AG poliinsaturados/saturados foi 0,82. As medias de AG w6 e w3 foram 23,41 e 5,63%. Os fatores sexo e MA nao influenciaram os poliinsaturados e colesterol (28,11mg/100g). A carne de capivara apresentou teores elevados de proteina e valores reduzidos de lipidios totais e de colesterol e relacao w6/w3 nutricionalmente adequada.

Physiological insights into Shechita.

The Government recently announced that it intends to reject a recommendation by the Farm Animal Welfare Council that all animals should be stunned before slaughter (see VR, April 10, p 446). In this Viewpoint article, Dr Stuart Rosen discusses physiological aspects of Shechita, the Jewish method of religious animal slaughter. He outlines the religious context and describes the act of Shechita. He discusses the scientific literature on the behavioural responses to Shechita as well as neurophysiological studies relevant to the assessment of pain, and concludes that Shechita is a painless and humane method of animal slaughter.

Dissemination of Brain Emboli following Captive Bolt Stunning of Sheep: Capacity for Entry into the Systemic Arterial Circulation

The epidemic of bovine spongiform encephalopathyin the United Kingdom and the recognition of a variant of Creutzfeldt-Jakob disease prompted revision of the guidelines for slaughter of cattle and sheep to prevent contamination of the edible parts of the carcass with central nervous system tissue. We previously showed that captive bolt gun stunning, which is routinely used for the slaughter of cattle and sheep, causes entry of fragments of central nervous system tissue into the jugular vein. To determine whether such tissue can traverse pulmonary capillaries to enter the systemic circulation, we introduced small volumes of brain tissue that had been disrupted by stunning with a captive bolt gun into the jugular vein of sheep sent for slaughter. We examined aortic blood samples by immunocytochemistry for neurofilament and S100 proteins and by enzyme-linked immunosorbent assay for glial fibrillary acidic protein and found fragments of neurofilament- and S100-immunopositive central nervous system tissue in samples from 2 of 11 sheep and elevated glial fibrillary acidic protein in 6 sheep. Our findings suggest that central nervous system tissue that is dislodged during routine captive bolt gun stunning and slaughter of sheep can enter the systemic arterial circulation and that, in some cases, this method of slaughter of an animal infected with bovine spongiform encephalopathy would be likely to contaminate edible parts of the carcass with infective material.

United States Department of Agriculture: building bridges through innovative animal well-being initiatives

AbstractAnimal well-being issues are addressed by the United States Department of Agriculture (USDA) through a variety of agencies and in various formats. Most farmers are good stewards of their animals and will raise them according to societal demands as supported by market choices. Management standards that are perceived to improve upon current practices are being demanded of farmers by buyers of animal products, including corporate restaurant chains and groceries. Professional organisations, USDA, and university representatives, help to address well-being issues and help to create and evaluate standards. The USDA provides leadership in several cooperative programs involving activists and industry, coordinates certification programs, and provides liaisons to multi-state university research committees. A USDA Animal Well-Being Work Group facilitates communications among agency personnel. The USDA developed the Animal Welfare Issues Compendium, a national animal well-being symposium, and cooperates with industry, activists and universities on projects. The USDA provides grant funds for projects that are encouraged to include a component on animal well-being. Special grant funds from Congress have resulted in educational and research projects that complement existing USDA national research and educational initiatives. Regulatory commitments by USDA include the enforcement of the Animal Welfare Act and the Humane Methods of Slaughter Act.

Assessment of some porcine strains as donors of islets of langerhans

Mass isolation of viable porcine islets is a difficult task because of their fragility, and because of donor variability with respect to strain, age, sex, feeding, and methods of slaughtering. Not all strains are equally suitable for islet separation. The aim of this study was to evaluate porcine pancreata as an alternative source of islets for clinical transplantation. Pancreata were digested from pig strains available in Poland: 248 market weight slaughterhouse pigs and 42 pigs, belonging to the Polish Large White (WBP, 14 sows and 3 males), Polish White Pendant-Ears (PBZ; 16 sows), Pietrain (8 sows), and Yorkshire (1 sow) races. Prepurification data of recoverable islets/g and islet equivalents/g were considered as representative for the number of recoverable islets. Acceptable results namely, islet and/or islet-equivalent (IE) number of at least 1000/g, were obtained from only 56 of 248 slaughterhouse pigs, namely 2073 ± 137.4 SE (median 1767/g) islets with values of IE of 2994 ± 303 SE (median 1874/g). Our data support Krickhahn et al suggesting that only pancreata with an average islet size exceeding 199 μm should be digested and that only from 1 of 3 to 5 porcine pancreata is an adequate amount of islets generated.

Metabolic rate and its relationship with ascites in chicken genotypes

1. Male chickens of 7 genetic lines, consisting of two pure sire and two pure dam populations, a commercial broiler cross and two slow-growing chicken lines (Label Rouge, LR and Mechelse Koekoek, MK) were reared from 1 to 37 d of age. The chickens received a two-phase dietary regime and were subjected to low ambient temperature. 2. The experimental aim was to investigate relationships between susceptibility to ascites and heat production. 3. Body weight gain (BWG), food intake and food conversion ratio (FCR) were determined. Ascites mortality, arterial pressure index (API=right ventricular/total ventricular weight ratio), haematocrit values, proportional lung weight (lung weight/body weight × 100), plasma thyroid hormones (thyroxine, T4 and triiodothyronine, T3) and arterial blood gas pressures ( pCO2 and pO2) were determined. The heat production per kg metabolic body weight (H/W0·75) and total heat production (H) were calculated for the period 16 to 33 d using an energy balance study according to the comparative slaughter method. 4. The two breeder sire lines had high BWG and low FCR and high but different incidences of ascites compared with the slow-growing ascites resistant LR and MK lines with notable high FCR. The broiler cross and slower-growing breeder dam lines had a similar and relatively lower incidence of ascites mortality. 5. The fast-growing chickens had low H/W0·75 values compared with slow-growing lines. 6. These fast-growing breeder sires had lower plasma thyroid hormone, reduced proportional lung weights, low arterial pO2 and high arterial pCO2 pressures compared with the slower-growing lines. 7. In conclusion, ascites incidence was associated with lower heat production per metabolic body weight and therefore a lower oxygen requirement per metabolic weight.

Electric stunning: a humane slaughter method for trout

The most common commercial slaughter method for portion-sized rainbow trout is asphyxiation in ice slurry. This method is however widely believed to expose the fish to unnecessary pain and suffering. The industry is consequently seeking an alternative method, which offers improved welfare of the fish at slaughter. Electric stunning of fish in water is identified as a suitable method. Parameters of an electric field that stuns trout beyond the point of recovery without causing carcass damage have been identified. A 60-s exposure to a 1000-Hz sinusoidal electric field of 250 V/m r.m.s. is recommended. Several practical options for implementing this method on commercial trout farms are identified and equipment for one of these approaches has been built and tested. The UK trout industry appears to be moving towards electric stunning as its preferred slaughter method.

Is humane slaughter of fish possible for industry?

Abstract The objective was to evaluate industrial and research slaughter methods for Atlantic salmon (Salmo salar), gilt-head seabream (Sparus auratus) and eel (Anguilla anguilla) with respect to welfare and quality. As a general term of reference, an optimal slaughter method should render fish unconscious until death without avoidable excitement, pain or suffering prior to killing. For Atlantic salmon, commercial slaughter methods (carbon dioxide stunning followed by gill cutting, and gill cutting alone) are not in conformity with the general term of reference, as the fish are not rendered unconscious immediately and possibly experience stress. Evaluation of automated percussive stunning remained unconclusive. More research should enable us to ascertain whether loss of consciousness is instantaneous. Electrical stunning can be humane if applied properly. However, because flesh of electrostunned fish was characterized by occasional bloodspots, optimization of the electrical parameters is required. Prototypes for percussive and electrical stunning of salmon have been recently developed. This implies that humane slaughter of salmon is feasible for industry. For gilt-head seabream, neither aphyxia in air nor transfer of the fish to an ice slurry were considered to be humane: the methods did not induce immediate brain dysfunction and vigorous attempts to escape occurred. Percussive and electrical stunning can be in conformity with the general term of reference. However, conditions for stunning whole batches of seabream have not been established. Quality of the fish slaughtered by percussive stunning was similar to that obtained by the industrial method, i.e. immersion in an ice slurry. Further work is required to establish optimal stunning conditions and to develop prototypes. For eel, desliming in a salt-bath followed by evisceration, electrical stunning performed under the conditions prescribed by the German legislation, and live chilling and freezing were not considered to be humane. In contrast, it was established that a 10–20 kg batch of eels in fresh water could be rendered unconscious immediately and until death by applying electricity in combination with nitrogen gas. The conditions used were 0.64 A dm−2 for 1 s, followed by 0.17 A dm−2 combined with nitrogen flushing for 5 min. A preliminary assessment of flesh quality suggests that it may be improved by application of the latter method, compared with the salt bath. The results clearly indicated that humane slaughter of eels is possible in practice.

Raw liver, singed sheep's head, and boiled stomach pudding: encounters with traditional Buriat cuisine

Indigenous to Inner Asia, Buriats are a formerly nomadic people who now reside in southern Siberia, in the areas east and west of Lake Baikal. Although settled members of the Russian Federation, their traditional cuisine reflects their nomadic roots. Milk and meat products – from horses, cattle, sheep, and goats – are still the two main components of the Buriats’ diet, supplemented by wild and cultivated plants (primarily hardy grains and root vegetables). Despite living within the dominant Russian culture, some Buriats still retain their shamanistic beliefs and make offerings to deities or spirits when drinking alcohol or eating certain foods. They have also preserved their ritual methods of slaughtering and butchering livestock, as well as traditional ways of processing the meat.

Evaluation of the growth parameters of six commercial crossbred pig genotypes 1. Under commercial housing conditions in individual pens

Simulation modelling is an active part of animal nutrition, which relies on mathematical functions to predict the performance of an animal. The Gompertz equation is one such function that is simple, but fits animal growth data well and when used in conjunction with allometry, can accurately predict the potential growth of an animal. When using this approach only three parameters are needed to sufficiently describe a genotype, viz. an estimate of mature size (protein weight at maturity - Pm), a rate of maturing (B) and an estimate of fatness (lipid:protein ratio at maturity - LPRm). The objective of this study was to estimate these parameters in South African commercial crossbred pigs under commercial environmental conditions. Thirty pigs each from six commercial genotypes were analysed using a serial slaughter method in which pigs were slaughtered at four and 14 days of age, and at 30, 40, 70, 80, 90 and 100 kg live weight. The animals were fed a choice between a high and low protein food and were housed in individual pens in two conventional open-sided housing facilities. The results indicated that there were no significant differences in mature weights or B of the various body chemical components between genotypes. This would support the use of a common set of growth parameters (B, Pm and LPRm of 0.0114±0.0005 /d, 40.0±1.86 kg, and 1.77±0.213 kg lipid/kg protein, respectively), inclusive of all commercial crossbred male pigs. However, the rate body lipid matures was significantly lower than the rate of other components within two genotypes. Evidence for the use of common allometric coefficients to define growth was inconclusive.

Effect of the slaughter method on the quality of raw and smoked eels (Anguilla anguilla L.)

Eels (Anguilla anguilla L.) were slaughtered using two procedures. The commercial method consisted of desliming the fish in dry salt followed by evisceration. The alternative method consisted of stunning and killing in water with a combination of electricity and oxygen removal. Eels slaughtered as commercially exhibited aversive reactions and consequently a higher level of muscular activity before death. In raw fillets, differences appeared clearly between the two batches. The alternative slaughter by electricity and gas led to redder, firmer flesh with a higher pH. Myofibrillar proteolysis, lipid oxidation and loss of freshness (as evaluated by K-value) were reduced. After hot-smoking, which is a process that greatly modifies the fish flesh properties, differences between batches were less pronounced. However, eels slaughtered by the alternative method were characterized by a higher pH and a redder colour of the dark muscle, a desirable property form a commercial point of view. When assessed by sensory difference tests, appearance seemed to be the only attribute that allowed panellists to discriminate the two batches. Overall, it is concluded that slaughter by electricity and gas improved the quality of raw and smoked eels compared with the commercial method.

Evaluation of slaughtering methods for turbot with respect to animal welfare and flesh quality

AbstractAfter elaborating a suitable scheme to assess consciousness/unconsciousness of turbot, the effects on fish welfare of commercial and experimental slaughtering techniques were evaluated. Strong adverse reactions and slow loss of clinical reflexes were observed when fish were slaughtered by bleeding without prior anaesthesia. The efficiency of electricity (150 V for 2 s followed by 25 V for 5 min) as a stunning and killing technique was dependent on the current frequency and mode of administration, ie whether the electrical discharge was applied to the head only or throughout the whole body. Finally, percussion of the head with a mechanical device resulted in immediate and permanent loss of all responses and reflexes in all fish tested. Three methods were selected as a result of the preliminary tests (bleeding in ice slurry, whole‐body electrical treatment and percussion), and their influence on flesh quality was studied over a 9 day period. Fish killed by percussion were characterised by a higher pH and higher water content in the very early stage of post mortem storage, but also by a much delayed rigor mortis. In contrast, fish killed by electricity entered most rapidly into rigor mortis; their flesh was significantly softer (p &lt; 0.05) throughout the entire storage time and was also redder and darker, as indicated by higher a* values (p &lt; 0.001) and lower L* values (p &lt; 0.01) respectively. It is suggested that automated percussion is a suitably humane method for the slaughter of farmed turbot.© 2002 Society of Chemical Industry

EFFECT OF SLAUGHTER METHOD ON DEGRADATION OF INTRAMUSCULAR TYPE V COLLAGEN DURING SHORT-TERM CHILLED STORAGE OF CHUB MACKEREL SCOMBER JAPONICUS

The present paper demonstrates that a nonstntggling slaughter method can delay degradation of type V collagen in meat of chub mackerel Scomber japonicus and softening of the meat during postharvest chilled storage. The fish were slaughtered by piercing a knife into nape (nonstruggling method) or by leaving on ground (struggling method) and then stored in an ice box. Sensory study revealed that the postharvest softening of the meat was moderated at 4 and 8 h by the non-struggling slaughter method in comparison with the struggling method. On the basis of the specific solubilization of type V collagen and reduced tyrosine content in it, a cleavage of the nonhelical regions (telopeptides) of the type V collagen occurred during the chilled storage in the fish slaughtered by the struggling method. The degradation of type V collagen was also slower in the meat of the fish slaughtered by the nonstruggling method, which can be directly linked to the moderation of the postharvest softening.

Fillet shelf-life of Atlantic halibut Hippoglossus hippoglossus L. fed elevated levels of α -tocopheryl acetate

Fish fillet quality may be influenced by the antioxidant level in preslaughter diet. Thus, the effects of dietary α-tocopheryl acetate supplementation and feeding time on the flesh quality of farmed Atlantic halibut Hippoglossus hippoglossus L. were investigated. Halibut of mean initial weight of 312 ± 12.3 g were divided into two groups and fed commercial diets, supplemented with different levels of α-tocopheryl acetate at the dietary inclusion levels of 189 and 613 mg kg−1 diet. Fish were sampled after 6,9,12 and 24 weeks. Over the experimental period, they reached a final mean weight of 1320 ± 108.4 g. Tissue α-tocopherol of fillet and liver was significantly affected by the levels of α-tocopheryl acetate given with the diets (P < 0.001). In storage on ice, fillets of fish fed the diets high in α-tocopheryl acetate exhibited significantly lower (P < 0.001) levels of lipid oxidation. The colour of fillets in all groups deteriorated slightly, but diet did not affect this process. Halibut fed the supplemented diets for longer periods were better protected against lipid oxidation (P < 0.001) and colour deterioration (P < 0.01) than those fed for shorter periods. However, after 9 days of storage, lipid oxidation levels were still extremely low [< 0.6 µg malondialdehyde (MDA) g−1 fillet], even in fillets of fish fed the low α-tocopheryl acetate diet for a short period preslaughter. Different slaughtering methods tested at the end of the trial showed that percussive stunning can delay the onset of rigor mortis by 8–12 h compared with bleeding of the fish. These results suggest that halibut fillets have enhanced shelf-life stability even at low doses of dietary α-tocopheryl acetate, and that other factors in the antioxidant defence mechanisms of the species might play a major role in the prevention of lipid oxidation.

Methods Used to Kill Fish: Field Observations and Literature Reviewed

AbstractThis paper reviews the impact on fish welfare of a wide range of slaughter methods used commercially around the world. Because the end result of the slaughter is a food product, and because of the well-known relationship between an animal's welfare and subsequent meat quality, the effects of the slaughter methods on the quality of the flesh are also reviewed where possible. Fish slaughter methods are incredibly diverse, but fall into two broad categories: those that induce loss of sensibility slowly, and those that achieve this rapidly. This paper shows that, in general, the methods that induce loss of sensibility over a long period of time tend to impinge more on the welfare of the animal and are detrimental to the overall quality of the carcass. Methods that cause a rapid loss of sensibility result in the best welfare, providing that they are carried out correctly. They may also produce the highest quality product from the stock offish.

Slaughtering method and dietary α -tocopheryl acetate supplementation affect rigor mortis and fillet shelf-life of turbot Scophthalmus maximus L.

The effects of dietary α-tocopheryl acetate supplementation and different slaughtering methods were investigated on the flesh quality of farmed market-size turbot Scophthalmus maximus (L). Turbot were divided into three groups and fed commercial diets, supplemented with different levels of α-tocopheryl acetate at the following dietary inclusion levels: 72 (100), 547 (500), 969 (1000) (mg of α-tocopheryl acetate kg−1 diet, analytical values with diet codes in brackets). After 5 months, fish (mean weight 1056 ± 19.7 g) from each dietary treatment were sampled, applying three different slaughtering methods: (A) bleeding in ice water; (B) thermal shock, no bleeding; (C) percussion followed by bleeding in ice water. The time course of rigor mortis was evaluated, using pH, rigor index and mechanical compression tests. The results showed that the three parameters corresponded very well. Percussive stunning resulted in higher initial post-mortem pH (P < 0.01) and a significantly delayed onset of rigor mortis (P < 0.05). Diet significantly affected shelf-life, with fillets from fish fed diets 500 and 1000 having lower TBARS (thiobarbituric acid reactive substances) numbers from day 2 (P < 0.001) and less colour deterioration from day 7 of storage on ice onwards (P < 0.05). These results suggest that an increase in dietary α-tocopheryl acetate before slaughter as well as careful selection of the slaughtering method may greatly enhance the flesh quality of market-size turbot.

Quality of farmed gilthead seabream ( Sparus aurata ) during ice storage related to the slaughter method and gutting

This paper examines the influence of the slaughter method and the post-mortem treatment (gutting) on the quality during ice storage of cultured gilthead seabream collected under industrial conditions. The choice of slaughter method had no great effect on the main biochemical indices, physicochemical parameters or sensory assessment, although there were slight microbiological differences. The expected improvement in quality using "humane" as opposed to commercial methods was not observed and was probably masked by the pre-slaughter stress affecting industrially harvested fish. The influence of gutting materialised as a decrease in the intensity of rigor mortis and a drop in microbial load, largely at the outset of shelf life. All the other parameters considered were almost unaffected by gutting. The physicochemical quality indices normally used to determine fish spoilage during ice storage are not suitable for establishing the quality of immature farmed gilthead seabream.

Evaluation of head-only and head-to-tail electrical stunning of farmed eels (Anguilla anguilla , L.) for the development of a humane slaughter method

The overall objective was to evaluate the suitability of electronarcosis as a stunning method for farmed eels. In the first experiment the minimum electrical current needed to induce a general epileptiform insult by head-only stunning was assessed. The individual eels (n = 40) with a live weight of 700–800 g were fixed in a specially designed re-strainer. The EEG (electroencephalogram) and ECG (electrocardiogram) recordings, observation of behaviour and responses to pain stimuli were used to assess unconsciousness, insensibility and cardiac function. The applied current of 150, 200 or 250 V, 50 Hz, AC was delivered via scissor-model stunning tongs for approximately 1 s. A general epileptiform insult was observed in 31 eels for which a successful EEG recording was obtained, using 255 ± 4 V, 545 ± 32 mA, for 1.2 ± 0.2 s. The general epileptiform insult as measured on the EEG was characterized by a tonic/clonic phase and an exhaustion phase. The behaviour showed one phase: tonic cramps alternated by clonic ones. The heart rate was 22 ± 8 beats min−1 (n = 23) prior to stunning. After stunning the ECG revealed fibrillation. In the second experiment the behaviour of seven individual eels able to move freely in water was observed after head-only stunning (250 V). Two phases were distinguished. Limited tonic and clonic cramps combined with backward swimming were followed by heavy clonic cramps combined with unco-ordinated movements such as jumping out of the water. A distinct exhaustion phase was not observed in all animals. In the third experiment a head-to-tail electrical method was examined in 15 eels for rendering the eels unconscious and insensitive prior to slaughter. They were stunned by applying 253 V for 3 s followed by 50 V for 5 min. In the fourth experiment nine eels were head-only stunned with 260 V for 1 s immediately followed by 50 V for 5 min applied from head to tail. Results obtained in these two experiments were similar. After stunning no brain activity and no responses to pain stimuli on the EEG were observed and the ECG showed ventricular extra systolae. It was observed that it might take 60 ± 25 min or longer for a complete recovery. It can be concluded that for effective electrical stunning of eels with a weight of 700–800 g an average current of 545 ± 32 mA (at approximate 250 V, 50 Hz AC) is needed. In this case, within a confidence level of 95% at least 91% of the eels are effectively stunned (n = 31). Therefore, it is recommended to increase the minimum current for an effective stun in practice to 600 mA. Further research is needed to determine the conditions to induce permanent unconsciousness and insensibility of the eels to protect the animals at slaughter.

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

The overall objective of the study was to evaluate a slaughter method of eels, which consisted of chilling until their body temperature was <5 °C for stunning, and subsequently placing them in cold brine at −18 °C for 15 min for killing. Three distinct experiments and a control were performed. 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 <5 °C was at least 5%. The heart rate decreased from 24±10 beats/min ( 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 <5 °C. Placing eels in brine water of −18 °C is an effective method to kill the eels before slaughter. However, it cannot be recommended to place conscious eels in cold brine water, because it takes more than 27 s before unconsciousness may be induced.

Electrical stunning of rainbow trout (Oncorhynchus mykiss): factors that affect stun duration

Many present commercial methods of slaughtering fish for food cause stress and aversive behaviour, which could be considered inhumane. This is especially true for rainbow trout (Oncorhynchus mykiss), which are usually slaughtered by removal from water resulting in death by anoxia. In the context of fish farming, this slaughter method is becoming less acceptable both from a welfare perspective and in terms of providing consistent and potentially improved flesh quality characteristics. The increasing concern for the welfare of fish has led to research to improve the situation. The use of electricity at slaughter could offer a humane procedure for stunning and/or killing large numbers of small fish when carried out correctly. This paper separately investigates the importance of stun application time, frequency and current magnitude of a sinusoidal alternating current on the ability to stun and stun/kill rainbow trout. In particular, increasing current magnitude and current application time were both found to increase the time for which the animals were effectively stunned. Also, above a current magnitude threshold, the trout were killed by the application. Increasing the frequency of the current waveform decreased the stun duration, until a threshold frequency was reached, at which it is suggested that it may not be possible to stun trout with the current parameters used. All three parameters need to be considered to ensure a humane stun or stun/kill, but such applications may also have implications for quality attributes of the flesh. This investigation will assist in the design of a humane electrical slaughter device for rainbow trout.