Stunning Procedure Research Articles

Assessing meat quality and textural properties of broiler chickens: the impact of voltage and frequency in reversible electrical water-bath stunning

The implementation of the head-only electrical stunning procedure in poultry processing has been aimed at enhancing eating, ethical, and religious quality. However, inconsistencies in voltage and frequency standardization, along with variations in previous research outcomes, have led to numerous cases of both under-stunned and over-stunned birds. Thus, this study aimed to comprehensively evaluate the effects of varying voltages and frequencies during electrical water bath stunning on carcass quality, meat attributes, and textural properties in broiler chickens. A cohort of 240 healthy female broilers (Cobb 500, 42-days-old, 2 kg ± 0.1 kg) was meticulously selected from a commercial farm. The birds underwent exposure to different stunning voltages (2.5, 10.5, 30, and 40 V) and frequencies (50 and 300 Hz). Subsequent analyses were conducted on meat samples to assess physicochemical properties, carcass quality, and textural attributes. The findings revealed a higher incidence of petechial hemorrhage (P < 0.05) in birds stunned at 10.5 V compared to other voltage. Notably, no broken bones were recorded in birds subjected to high voltages (30 and 40 V). Low frequency (50 Hz) significantly increased the occurrence of petechial hemorrhage and simultaneously resulted in pectoralis major muscle with decreased redness (a*). Birds subjected to the 10.5 V stunning treatment exhibited a lower cooking loss percentage. Significant interactions between voltage and ageing (V × A) were observed. Birds stunned at 30 V and aged for 7 d displayed highest drip loss compared to a one-day ageing period across different voltage levels. This interaction also impacted pH values, with birds subjected to 10.5 V showing significantly lower (P < 0.05) pH at d 7 of ageing. The meat hardness was influenced by the V × A interaction, wherein birds stunned at 10.5 V exhibited lower hardness after one day of ageing compared to other voltage levels. Red wing tips, lightness (L*), adhesiveness, and resilience were also significantly impacted (P < 0.05) by the interaction between frequency and voltage. A notable 3-way interaction was observed for gumminess and chewiness (F × V × A), where the 2-way interaction between frequency and voltage (F × V) affected both parameters differently at various ageing periods. Additionally, there was a significant interaction (P < 0.05) between frequency and voltage influencing shear strength and yellowness.

Highly Effective Frontal Stunning Procedure Using a Pneumatic Penetrating Captive Bolt in Water Buffaloes

An effective frontal stunning procedure in water buffaloes was assessed using a pneumatic penetrating captive bolt (PPCB) with high air pressure. The study contemplated two phases; first, 352 buffaloes and 168 post-mortem heads were evaluated to determine the most effective anatomical site for stunning. Then, the second phase (n = 182) was used to validate the stunning procedure at the discovered anatomical site in the first phase, which was located 8 cm dorsal above the middle of the forehead on an "X" formed between the eyes and the base of the contralateral horns, and 2 cm lateral, avoiding the midline, where the skull tended to narrow. A total of 95.1% of buffaloes received effective stunning at the first shot with evidence of the presence of collapse, absence of rhythmic breathing, and absence of ocular reflexes (corneal and palpebral). There were no differences in the stunning efficacy by sex, breed, or skull thickness. These findings demonstrated that stunning with a PPCB at pressures of 1379-1516.8 KPa (200-220 pounds per square inch (psi)) in the site reported here produces a highly effective stunning at the first shot in water buffaloes.

Head-Only Stunning of Turkeys Part 2: Subjective and Objective Assessment of the Application of AC and DC Waveforms.

Simple SummaryIn this study, we investigated various types of application of head-only electrical stunning to turkeys, in order to improve the effectiveness of the stunning process. We used recordings of physical responses and of electroencephalograms (EEGs) to assess effectivity of stunning and various waveforms: alternating current (AC) and pulsed direct currents (DC). Depending on the waveforms, voltages between 125 and 250 V produced an effective stun in turkeys in this study.Electrical stunning is likely to remain an important stunning method for turkeys at slaughter. The purpose of this study is to understand the application of various waveforms of alternating current (AC) and pulsed direct currents (DC), head-only, to turkeys and to improve the effectiveness of handheld stunning of turkeys. We evaluated the effectiveness of stunning by documenting physical responses and recording electroencephalograms (EEGs). For the assessment of physical responses, the stunning voltage was varied depending on the proportion of animals effectively stunned at a certain voltage level. If all turkeys in a group of 10 were stunned, the voltage was decreased, and the next group was stunned. This was repeated until not all turkeys showed signs of being effectively stunned. The experiment was then repeated at the voltage level just above the one that showed incomplete effective stunning. The effects of the stunning on the EEG recording was assessed in 16 turkeys to measure the occurrence of epileptiform EEGs, in 14 turkeys to assess epileptiform EEGs after neck-cut (bleeding), and in 14 turkeys to assess the effect of increased voltage and reduced frequency on epileptiform EEGs. Assessing EEGs in a laboratory setting contributes considerably to the understanding of electrical stunning procedures. Voltages between 125 and 250 V, depending on the waveform assessed, were effective in producing an effective stun in turkeys in this study.

Magnetic resonance imaging and computer tomography of brain lesions in water buffaloes and cattle stunned with handguns or captive bolts

Owing to the demand for genuine mozzarella, some 330 water buffaloes are being slaughtered every year in Switzerland albeit a stunning procedure meeting animal welfare and occupational safety requirements remains to be established. To provide a basis for improvements, we sized anatomical specifics in water buffaloes and cattle and we assessed brain lesions after stunning with captive bolts or handguns by diagnostic imaging. In water buffaloes and cattle, the median distance from the frontal skin surface to the inner bone table was 74.0mm (56.0–100.0mm) vs 36.6mm (29.3–44.3mm) and from skin to the thalamus 144.8mm (117.1–172.0mm) vs 102.0 (101.0–121.0mm), respectively. Consequently, customary captive bolt stunners may be inadequate. Free bullets are potentially suitable for stunning buffaloes but involve occupational safety hazards. The results of the present study shall be used to develop a device allowing effective and safe stunning of water buffaloes.

Pre-slaughter conditions, animal stress and welfare: current status and possible future research

The present paper describes the main procedures used to slaughter fowl, pigs, calves and adult cattle, sheep, and farmed fish, starting on the farm and ending with the death of the animal at the abattoir. It reviews the currently known causes of stress, indicated by behavioural and physiological measurements on the animal level, and by post-mortem muscle metabolism. During the pre-slaughter period, psychological stress is due to changes of environment, social disturbances and handling, and physical stress is due to food deprivation, climatic conditions, fatigue, and sometimes pain. The exact causes of stress depend, however, on the characteristics of each species, including the rearing system. For fowl, bird catching and crating, duration and climatic conditions of transport and of lairage and shackling are the main known pre-slaughter stress factors. For pigs, stress is caused by fighting during mixing of pens, loading and unloading conditions, and introduction in the restrainer. Handling and novelty of the situation contribute to the stress reactions. For veal calves and adult cattle, disruption of the social group, handling, loading and sometimes unloading conditions, fatigue, novelty of the situation and for calves mixing with unfamiliar animals are known stress factors. Gathering and yarding of extensively reared lambs and sheep causes stress, particularly when shepherd dogs are used. Subsequent transport may induce fatigue, especially if sheep are commercialised through auctions or markets. In farmed fish, stress is predominantly related to environmental aspects such as temperature, oxygen, cleanliness of the water and, to a certain extent, stocking density and removal of the fish from the water. If transport and lairage conditions are good and their durations not too long, they may allow pigs, calves and adult cattle, sheep, and fish to rest. For certain species, it was shown that genetic origin and earlier experience influence reactions to the slaughter procedure. Stunning techniques used depend on the species. Pigs and fowl are mostly electrically or gas-stunned, while most adult cattle are stunned with a captive bolt pistol. Calves and sheep may be electrically stunned or with a captive bolt pistol. Various stunning methods exist for the different farmed fish species. Potential causes of stress associated with the different stunning procedures are discussed. The paper addresses further consequences for meat quality and possible itineraries for future research. For all species, and most urgently for fish, more knowledge is needed on stunning and killing techniques, including gas-stunning techniques, to protect welfare.

Electrical and percussive stunning of the common carp (Cyprinus carpio L.): Neurological and behavioural assessment

The overall objective of the study was to evaluate electrical and percussive stunning methods under laboratory conditions in common carps. The electrical current needed to induce a general epileptiform insult was assessed in 13 carps. The insult was obtained by delivering a current of 0.24±0.03A (163±1 V; 50Hz, a.c.) to the head, via scissor-model stunning tongs for approximately 1s. The duration of the tonic, the clonic and the exhaustion phases were 11±4s, 5±3s and 20±14s on the EEG, respectively. An actual clonic phase was observed in two fish. The total duration of the insult was 31±14s. The heart rate was 22±12beats/min prior to stunning while after stunning, the ECG revealed fibrillation for 18±7s and was irregular. The behaviour of 10 individual carp, which were allowed to move freely in water, was recorded following head-only stunning (164V, 0.23±0.6A). The duration of the tonic phase was approximately 10s and the fish started fin movements after 48±8s and resumed swimming after 121±83s. A general epileptiform insult could be induced in carps (n=25) by passing an electrical current through fresh water using 0.14±0.03A/dm2 (113±17V; electrode distance 16cm) for 1s at a water conductivity of 200μS/cm. Twenty three carps were rendered unconscious and insensible during electrical stunning in fresh water, using 0.73±0.05A/dm2 (411±2 V; electrode distance 16cm) for 5s at a water conductivity of 330μS/cm, followed by chilling in ice water. As a second stunning procedure, carps were stunned mechanically using a percussion pistol at a maximal velocity of 10.99±0.88J. Evidence of unconsciousness and insensibility of the carps was provided by the appearance of theta, delta waves and spikes on the EEG, which were proceeded by no brain activity. However, two carp responded after 0.5min to administered pain stimuli and one carp after 3min. It may be concluded from this study that common carp are effectively stunned in fresh water. The application of an electrical current of 0.73A/dm2 (26V/cm, 50Hz, a.c., 330μS/cm) to individual carps in a tank in combination with chilling in ice water is an effective procedure for slaughter. The mechanical method of percussion stunning did not provide assurance of effective stunning as not all carp were unconscious and insensible after its administration.

Effect of different slaughtering methods on death time of Daglic breed lambs

In this study, 80 Daglic race, male 8-month-old sheep were used as material. The sheep were seperated in 4 groups. The sheep in the group 1 were slaugthered in horizantal position and non - stunned. The sheep in group 2 were slaughtered in vertical position and non-stunned. The head-only stunning procedure was applied to the third group and the sheep were stunned in horizantal position. Group 4 sheep were slaughtered in vertical position after the head-only stunning procedure was applied. According to the obtained results, bleeding time, total blood amount, live weight ,and percent of total blood parameters were significantly different among the groups. It is important to apply stunning applications for the welfare of the slaughtering farm animals. Also, the quality of meat and its products is directly related with the bleeding time and total amount of bleeding parameters.

Recent developments in stunning and slaughter of poultry

A requirement under humane slaughter regulation is that stunning methods should induce immediate loss of consciousness and sensibility. If the onset of unconsciousness is not immediate, the induction of unconsciousness with a stunning method should not cause in animals avoidable anxiety, fear, pain, distress or suffering. The duration of unconsciousness induced by a stunning procedure must be longer than the sum of time that lapses between the end of stun and the time to onset of death. Since the effect of a stunning method is momentary, the onus of preventing resumption of consciousness thereafter relies on the efficiency of slaughter procedure; i.e. the prompt and accurate severance of blood vessels supplying oxygenated blood to the brain. Electrical water baths and gas or controlled atmospheres are commonly used for stunning poultry under commercial conditions. The electrical waveforms (sine wave alternating current or pulsed direct current) and frequencies (Hz) employed to stun poultry and the amount of current applied to individual birds in a water bath stunner widely varies. Rationalisation of electrical variables is urgently warranted. Varieties of gas mixtures have been proposed or used for stunning or killing poultry in crates or conveyors however the bird welfare implications have not been communicated effectively to facilitate progress.This review deals with the efficacy of electrical variables used in the water baths and of slaughter methods, and the relative merits of different gas mixtures used for stunning or killing broilers.

Recent developments in stunning and slaughter of poultry

A requirement under humane slaughter regulation is that stunning methods should induce immediate loss of consciousness and sensibility. If the onset of unconsciousness is not immediate, the induction of unconsciousness with a stunning method should not cause in animals avoidable anxiety, fear, pain, distress or suffering. The duration of unconsciousness induced by a stunning procedure must be longer than the sum of time that lapses between the end of stun and the time to onset of death. Since the effect of a stunning method is momentary, the onus of preventing resumption of consciousness thereafter relies on the efficiency of slaughter procedure; i.e. the prompt and accurate severance of blood vessels supplying oxygenated blood to the brain. Electrical water baths and gas or controlled atmospheres are commonly used for stunning poultry under commercial conditions. The electrical waveforms (sine wave alternating current or pulsed direct current) and frequencies (Hz) employed to stun poultry and the amount of current applied to individual birds in a water bath stunner widely varies. Rationalisation of electrical variables is urgently warranted. Varieties of gas mixtures have been proposed or used for stunning or killing poultry in crates or conveyors however the bird welfare implications have not been communicated effectively to facilitate progress. This review deals with the efficacy of electrical variables used in the water baths and of slaughter methods, and the relative merits of different gas mixtures used for stunning or killing broilers.

The influence of RN genotype, including the new V199I allele, on the eating quality of pork loin

The eating quality of M. longissimus dorsi (LD) from RN − homozygotes, RN − heterozygotes and RN − non-carriers was investigated in a Swedish Hampshire×Finnish Landrace pig population. The recently identified new allele (V199I, here denoted rn*) at the RN locus was also detected among the pigs selected and included in the sensory evaluation. The number of animals varied from 10 to 15 in the five genotype groups; RN −/ RN −, RN −/ rn+, RN −/ rn*, rn+/ rn+ and rn+/ rn* (in total 59 pigs). In addition, one pig was determined to be rn*/ rn* but was excluded from the analysis. The three genotypes in which the RN − allele was represented ( RN −/ RN −, RN −/ rn+ and RN −/ rn*) had higher glycogen and lower protein contents as well as lower ultimate pH (measured 48 h post-mortem) in LD than the non-carriers ( rn+/rn+ and rn+rn*). Of the sensory parameters evaluated (tenderness, chewing time, chewing residual, juiciness, meat flavour and acidity), the five RN genotypes only affected acidity significantly; the RN − allele contributing to a more acid taste in LD. The influence of the rn* allele resembled that of rn+ on the sensory parameters. When the material was divided into three groups (homozygous, heterozygous and non-carriers of the RN − allele) the juiciness was found to be significantly influenced by RN genotype, and LD from animals that were homozygous and heterozygous with respect to the RN − allele exhibited a higher juiciness than LD from non-carriers. The RN − allele also tended to contribute to greater tenderness, which was significantly higher in LD from heterozygous carriers than from non-carriers of the RN − allele. A more rapid decline in pH (measured as pH at 45 min and 3 h post-mortem) contributed to a greater tenderness in LD (according to a trained panel and Warner-Bratzler shear force). In addition to the RN genotype, the decline in pH was influenced by carcass weight, which varied between 71 and 97 kg, and by stunning procedure, which changed during the course of the study from individual to group stunning with CO 2. The individual stunning procedure contributed to a lower pH in the initial post-mortem phase (pH 45), whereas a higher carcass weight and the RN − allele lowered the pH in the mid-post-mortem region (pH 3h and pH 24h), significantly ( P⩽0.05). The pH continued to decline after 24 h post-mortem and the ultimate pH was not reached until 48 h post-mortem. The cooking loss, juiciness and acidity were related to the specific characteristics of the RN − carriers, such as higher glycogen content, lower protein content and lower ultimate pH (pH 48h).

A feasible method for humane slaughter of eel (Anguilla anguilla L.): electrical stunning in fresh water prior to gutting

It was observed that farmed eels could be rendered unconscious and insensible instantaneously by passing an electrical current through fresh water. The general epileptiform insult on the EEG was characterized by a tonic/clonic and an exhaustion phase. After stunning, the ECG (electro-cardiogram) revealed fibrillation. The electrical stunning parameters were on average 194 ± 4 V and 0.636 ± 0.040 A/dm2 for 1.6 ± 0.4 s. Within a confidence level of 95%%, taking into account the number of animals with a reliable EEG (n = 29), at least 93% of all eels are effectively stunned in fresh water by an average current of 0.636 ± 0.040 A/dm2. The behaviour of groups of five eels, which were able to move freely in the water was observed before and after stunning with 50 V and 0.17 A/dm2. After 3-s stunning, two eels were turned upside down. They changed to a normal position after 10 and 13 s respectively. Subsequently, all eels were very active in swimming behaviour and stopped swimming after 75 s. When stunned for a longer duration, all eels were turned upside down and stopped breathing for a limited period of time. In the last experiment the eels were stunned in fresh water (500 μS) with a voltage of 200 V for approximately 1 s, which was followed by 50 V for 5 min. As soon as the stunning started the water was de-oxygenated by flushing nitrogen to kill the eels by suffocation during the period of unconsciousness and insensitivity. The oxygen saturation decreased from 74 ± 10 to 23 ± 11% at 22 °C. After stunning no brain activity and no responses to pain stimuli were observed on the EEG. The heart rate increased (P < 0.05) after stunning, which was followed by a significant decrease. Only 1 out of 18 eels returned partially from upside down to a normal position 2 h after stunning; however, the eel did not respond to pain stimuli in behaviour. The developed stunning procedure can be recommended for humane slaughter of 50-kg batches of eels.

Rigor mortis development in turkey breast muscle and the effect of electrical stunning

Rigor mortis development in turkey breast muscle and the effect of electrical stunning on this process are not well characterized. Some electrical stunning procedures have been known to inhibit postmortem (PM) biochemical reactions, thereby delaying the onset of rigor mortis in broilers. Therefore, this study was designed to characterize rigor mortis development in stunned and unstunned turkeys. A total of 154 turkey toms in two trials were conventionally processed at 20 to 22 wk of age. Turkeys were either stunned with a pulsed direct current (500 Hz, 50% duty cycle) at 35 mA (40 V) in a saline bath for 12 seconds or left unstunned as controls. At 15 min and 1, 2, 4, 8, 12, and 24 h PM, pectoralis samples were collected to determine pH, R-value, L* value, sarcomere length, and shear value. In Trial 1, the samples obtained for pH, R-value, and sarcomere length were divided into surface and interior samples. There were no significant differences between the surface and interior samples among any parameters measured. Muscle pH significantly decreased over time in stunned and unstunned birds through 2 h PM. The R-values increased to 8 h PM in unstunned birds and 24 h PM in stunned birds. The L* values increased over time, with no significant differences after 1 h PM for the controls and 2 h PM for the stunned birds. Sarcomere length increased through 2 h PM in the controls and 12 h PM in the stunned fillets. Cooked meat shear values decreased through the 1 h PM deboning time in the control fillets and 2 h PM in the stunned fillets. These results suggest that stunning delayed the development of rigor mortis through 2 h PM, but had no significant effect on the measured parameters at later time points, and that deboning turkey breasts at 2 h PM or later will not significantly impair meat tenderness.

Factors affecting the effectiveness of head-only electrical stunning in sheep

The effects of factors such as the position of the tongs, the presence of wool, and the wetness of the skin on the efficiency of the head-only stunning procedure, and...

Some neural and behavioural aspects of electrical and mechanical stunning in ostriches

Different electrical and mechanical stunning procedures were studied in ostriches to determine the effectiveness of the method. Fifty-eight South-African Black ostriches were equipped with EEG electrodes and stunned with three different electrical head-only methods and with a new captive needle pistol, using air pressure. The first stunning procedure consists of two trials. In the first trial a total of 45 ostriches were stunned with a voltage of 200 V (spiked electrodes) during 1 s. Unfortunately, in 10 animals the electrodes were disconnected. A general epileptiform insult on the EEG followed by recovery was observed in 20 ostriches. Another eight animals died after recovery and five showed an iso-electric line and were dead. The total duration of the insult was 25±10 s. The measured current was 463±120 mA. In the second trial a constant current of 400 mA was administered to 13 ostriches. In one animal the electrodes were disconnected. Eight out of 12 animals showed a general epileptiform insult, two of them showed an iso-electric line and two did not show the characteristics of a general epileptiform insult. The total duration of the insult on the EEG was 21±8 s. The measured current was 365±91 mA and the voltage 191±27 V. During the second stunning procedure four and seven ostriches were stunned with 200 V (spiked electrodes) and 48 V (blunt electrodes), respectively, during approx. 6 s. They all died. In addition, a group of 20 ostriches stunned with captive needle pistol using air pressure showed unconsciousness after stunning by the appearance of theta and delta waves tending to an iso-electric line on the EEG trace. It is recommended to use at least 500 mA to stun ostriches effectively and to use a short stun-stick interval or to kill them by a long stunning duration. The captive needle pistol, using air pressure, can be an alternative for electrical head-only stunning.

Meat and carcass quality in two pig lines of different stress-susceptibility genotype and their crosses

AbstractIn order to investigate differences in carcass and meat quality between lines of different stress susceptibility, 150 pigs were slaughtered on 15 slaughter days, consisting of equal numbers of stress-susceptible (nn) pigs of a boar line, stress-resistant (NN) pigs of a sow line and stress-carrier (Nn) crosses of these two lines. Carcass quality was determined by a SKGII-device which combined four physical measurements into a carcass lean estimate and a conformation score, and meat quality traits were measured on the carcass and on a loin slice. Killing-out proportion was lower for the NN line compared with the Nn crosses and the nn line. Lean content increased and conformation score improved as the number of n alleles in the respective genotypes increased but the Nn genotype was closer to the nn genotype than to the NNgenotype. Similarly, a large difference in meat quality was found between the NN and the nn line, whereas the difference in meat quality between the Nn and the nn genotype was smaller than expected. This was probably due to the low-voltage stunning procedure. In addition, the method of transporting the pigs to the abattoir (by truck or by foot, for a distance 125 m) had a pronounced effect on meat quality in the loin.

Causes for variation in pork quality

Research was carried out on 260 pigs that were slaughtered in 12 batches in the slaughter facilities of ID-DLO at Zeist. The practical circumstances were highly standardized. The ‘animals’ meat quality was good with only little variation; 46 animals showed a ‘slightly’ aberrant quality and 6 ‘slight’ DFD. Carcasses within the quality categories ‘PSE’ and ‘slight’ PSE did not occur. Statistically significant effects on meat quality could be shown for the duration of the resting period before slaughter and the muscular contractions occurring while stunning, shackling and exsanguination, despite the minor variation in pork quality under standardization. A longer resting period before slaughter induced significantly lower temperatures in the m. semimembranosus and the loin at 45 min post mortem and a slightly higher ultimate pH, accompanied by a somewhat darker colour (24hr post mortem). A connection between the animal's behaviour at the fattening station and ultimate pork quality could not be shown. The same counts for fighting in the resting pen of the slaughter house and the pig's behaviour in the stunning area. Muscular contractions during and after stunning had a negative effect on pork quality, causing a more rapid drop in pH, a faster development of rigor mortis and a reduced water holding capacity. An imperfect electrical stunning procedure caused an increase in muscular contractions.

Effects of normal, light/normal or double stunning on the incidence and severity of blood splash in lambs

One-hundred-and-twenty lambs were divided into three equal groups which were subjected to head electrical anaesthesia before bleeding. The normal group was stunned and bleeding was initiated within 5 to 8 s. The light/normal group was partially stunned and then treated as the normal group after a delay of 10s. The double stunned group was electrically anaesthetised, allowed to recover and then restunned and bleeding was initiated within 5 to 8 s. The light/normal and double stunning procedures increased the incidence and severity of carcass blood splash compared with normal stunning but the increase was less than that sometimes seen in normal mobs of head-stunned sheep and which occurs for unknown reasons.

Influence of ante‐ and peri‐mortem factors on biochemical and physical characteristics of turkey breast muscle

Summary The course of post-mortem breakdown of glycogen and ATP in turkey pectoralis major muscle was markedly influenced by several ante- and peri-mortem variables. Application of a proper stunning procedure was highly effective in preventing peri- and post-mortem muscle stress reactions. The physiological level of glycogen and ATP was not significantly affected by road transportation covering 260 km. Birds which rested for 24 hrs following transportation had lower glycogen and ATP levels at the moment of slaughter than non-rested birds. According to the changes in the rate and extent of post-mortem biochemical reactions, several meat characteristics such as water-holding capacity, colour, and tenderness were significantly changed. Furthermore, the results also indicate that turkey breast muscle is susceptible to a PSE-like condition as described in pork.