A bespoke management package can reduce levels of injurious pecking in loose-housed laying hen flocks.

This study investigated the protective effects of an on-farm management package designed to reduce injurious pecking (IP) in loose-housed laying hens. A systematic review of scientific literature generated 46 potentially protective management strategies. Bespoke management packages were designed for treatment flocks (TF) using these management strategies. IP in 53 TFs was compared with IP in 47 control flocks (CF) where the management package was not employed. Scoring of plumage damage (PD) and observations of gentle and severe feather pecking (GFP; SFP), and vent and cannibalistic pecking (VP) were completed, and management strategy use was recorded, at 20, 30 and 40 weeks of age. Differences between treatment and CF were examined using multilevel modelling. Compared with CF, TF employed more management strategies (P<0.001), had lower PD (P=0.003) and SFP (P=0.019). Regardless of treatment or control flock status, the more of the 46 management strategies that were employed the lower was the PD (P=0.004), GFP (P=0.021), SFP (P=0.043), mortality at 40 weeks (P=0.025), and the likelihood of VP (P=0.021). Therefore, the provision of a bespoke management package was protective against the majority of forms of IP in commercial laying hen flocks.

Influence of housing system and design on bone strength and keel bone fractures in laying hens.

The main objectives of the study were to provide an accurate assessment of current levels of old breaks in end-of-lay hens housed in a variety of system designs and identify the important risk factors. Sixty-seven flocks housed in eight broad subcategories were assessed at the end of the production period. Within each flock, the presence of keel fractures was determined and the tibia, humerus and keel bones dissected for measurement of breaking strength. For each house, variations in internal design and perching provision were categorised and the effective heights of the differing structures recorded. All systems were associated with alarmingly high levels of keel damage although variation in mean prevalence between systems was evident with flocks housed in furnished cages having the lowest prevalence (36 per cent) despite also having significantly weaker bones and flocks housed in all systems equipped with multilevel perches showing the highest levels of damage (over 80 per cent) and the highest severity scores.

Brain tissue fragments in jugular vein blood of cattle stunned by use of penetrating or nonpenetrating captive bolt guns.

Although the incidence of bovine spongiform encephalopathy in cattle continues to decline in the United Kingdom, it remains important to maintain vigilance of all potential routes of transmission of infection to humans. Initial studies have demonstrated a potential risk of carcass contamination with brain tissue following the use of captive bolt gun stunning in cattle. The objective of this study was to further explore these initial findings particularly in regard to captive bolt guns currently in use in the United Kingdom. Brain tissue fragments or elevated levels of a marker protein for brain tissue were detected in venous blood samples from 4% (95% confidence interval, 1.6 to 9.8%) of cattle stunned by penetrating captive bolt gun and from 2% (95% confidence interval, 0.6 to 7%) of those stunned by nonpenetrating captive bolt gun.

Dissemination of brain emboli following captive bolt stunning of sheep: capacity for entry into the systemic arterial circulation.

The epidemic of bovine spongiform encephalopathy in 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.

The effect of repeat application of electrical stunning on the welfare of pigs.

Although legislation requires the production of immediate insensibility, implying that a stun can be applied only once, the practice of repeat application of electrical stunning is common. However, the relative consequences of such repeat applications are unknown. This study investigated the effects of repeat applications of electrical stunning (200 V, 50 Hz) following different delays of 15, 60 or 180 s between the initial stun and the repeat applications. The parameters examined, following stunning, were the durations of spontaneous physical activity, time to return of reflexes and the duration of the epileptiform activity in the electrocorticogram. The results showed that repeat application of electrical stunning can produce successive epileptic activity and therefore an effective stun. The duration of tonic and clonic phase activity following repeat application was significantly shorter than after a single stun only. There was a tendency for the reflexes to return more quickly following repeat application. The use of electrical stunning to re-stun pigs appears to raise no welfare concerns and although commonly used, should only be applied out of necessity rather than as routine practice.

Jugular venous emboli of brain tissue induced in sheep by the use of captive bolt guns.

Emboli of central nervous tissue were detected in the jugular venous blood of two of 15 sheep stunned with a conventional cartridge-operated captive bolt gun and in two of 15 sheep stunned with a pneumatically activated gun. No emboli were detected in arterial blood from these sheep or in venous blood from sheep stunned electrically. Emboli from an animal with BSE could transmit the disease to people.

Commercial slaughter methods used on Atlantic salmon: determination of the onset of brain failure by electroencephalography.

This study investigated the effect of exsanguination without prior stunning, or carbon dioxide narcosis followed by exsanguination, or percussive stunning or spiking the brain, on the time taken to abolish the visual evoked responses (VERS) of farmed Atlantic salmon. Only percussive stunning and spiking killed the fish immediately and the other two methods resulted in aversive reactions by the fish. The VERS were lost between 148 and 440 seconds after exsanguination without stunning, and between 300 and 554 seconds after carbon dioxide narcosis followed by exsanguination. During both these procedures the fish showed strong aversive behaviour. In contrast, percussive stunning and spiking the brain could result in the immediate loss of VERS and no aversive reactions from the fish if the stun was applied correctly.

Methods for detection of haematogenous dissemination of brain tissue after stunning of cattle with captive bolt guns.

Because of concern that the stunning of cattle with captive bolt guns (CBGs) could, if used on an animal with bovine spongiform encephalopathy (BSE), cause embolism of infective brain tissue and carcass contamination, the Ministry of Agriculture, Food and Fisheries commissioned research to assess the risk of haematogenous dissemination of CNS material after stunning. We have devised two methods to investigate this risk. The first involves the concentration of embolic tissue in buffy coat Cytoblocks that can be embedded for sectioning, microscopy and immunocytochemistry. The second method is an ELISA for the presynaptic protein, syntaxin 1B. The methods were validated by analysis of several bovine tissues, including blood samples deliberately contaminated with brain. We then studied jugular venous blood obtained before and after the stunning of 60 cattle with CBGs. Samples obtained, after stunning, from five of the cattle contained CNS tissue within the Cytoblocks and yielded positive syntaxin assays. Syntaxin was also detected in samples from one other animal that had been stunned with a pneumatically operated CBG. The described methods should allow an assessment of the risk of neuroembolism associated with different types of CBG and may also be useful in other contexts.

Evaluation of electrical stunning in commercial rabbits effect on brain function.

Effect of electrical stunning on brain function in commercial rabbits was evaluated in electrophysiological studies. In addition to measuring duration of spontaneous physical activity and times to signs of recovery, electrocorticogram (ECOG) recordings and evoked responses were analysed following electrical stunning with 100 V for 1 s in eight rabbits. Epileptiform and other types of activity indicating insensibility were observed in the ECOG. Evoked responses were absent from 24 to 204 s following stunning. Application of a minimum current of 140 mA followed by prompt sticking should prevent welfare problems at stunning and slaughter in rabbits.

The effect of the sticking method on the welfare of slaughter pigs.

A project was undertaken to investigate the causes of inadequate sticking encountered during a survey of pig abattoirs. The results of the investigation identified the length of the sticking (exsanguination) wound as a major contributor to the problem. Experimental abattoir trials conducted on slaughter pigs comparing two sticking lengths indicated that the rate of bleed out was delayed with short sticking wounds. In addition, information about the identity of blood vessels severed following sticking was obtained. The results indicate that following head-only electrical stunning, a relatively long sticking wound should provide better welfare in slaughter pigs. The study has also highlighted the health and safety problems for the operatives as well as the welfare concerns associated with manual application of electrical stunning.

Variations in electrical stunning tong placements and relative consequences in slaughter pigs.

Variations in the manual application of electrical stunning tongs that are commonly observed in stunning pens in abattoirs were tested under laboratory conditions on 145 pigs. Five different placements, previously identified during a survey, using either 150 or 250 V were studied, and the welfare consequences and effects on the intensity of carcass convulsions were assessed. Quantitative relationships between tong applications, average current strength, prevalence of induction failure, indicators of insensibility and signs of recovery were evaluated. Those placements not spanning the brain were found to be inadequate on welfare grounds when used at 150 or 250 V. The variation in convulsion intensity, subjectively scored, was small and therefore it is unlikely that tong position using a 50 Hz alternating current (AC) is an important factor influencing carcass handling. The need to develop methods for reliably measuring currents going through the brain is emphasized.

Changes in the somatosensory evoked potentials and spontaneous electroencephalogram of broiler chickens during exposure to gas mixtures.

1. Six week-old broiler chickens implanted with electroencephalogram (EEG) recording and somatosensory stimulating electrodes were exposed to either 90% argon in air, a mixture of 30% carbon dioxide and 60% argon in air or a mixture of 30% oxygen and 40% carbon dioxide (balance nitrogen) for 2 min, to determine the times to onset of changes in spontaneous EEG and the loss of somatosensory evoked potentials (SEPs) and thus unequivocal loss of consciousness. 2. In addition, after a 2 min exposure to the carbon dioxide-oxygen mixture, some broilers were allowed to recover in air and their EEGs and SEPs were continuously recorded until the return of normal EEG and SEPs. During this period, the time to return of response to comb pinching was also determined in 10 broilers. 3. All broilers exposed to either argon or the carbon dioxide-argon mixture died within 2 min, whereas, only 3 out of 17 broilers died during the 2 min exposure to the carbon dioxide-oxygen mixture. 4. During exposure to argon, unlike the other 2 gas mixtures, the majority of broilers showed high amplitude, low frequency electrical activity in the EEG on average at 10 s. The mean times to onset of EEG suppression were 17, 19 and 40 s after exposure to argon, the carbon dioxide-argon mixture and the carbon dioxide-oxygen mixture, respectively. An isoelectric EEG occurred on average at 58 and 41 s after exposure to argon and the carbon dioxide-argon mixture, respectively. An isoelectric EEG did not occur in broilers which were exposed to the carbon dioxide-oxygen mixture. 5. The SEPs were abolished in broilers on average 32 and 24 s after exposure to argon and the carbon dioxide-argon mixture, respectively. During exposure of broilers to the carbon dioxide-oxygen mixture the SEPs were abolished in the majority of birds on average at 47 s, however, 2 out of 14 birds retained their SEPs for the entire period of 2 min exposure to this gas mixture. 6. During the recovery after exposure to the carbon dioxide oxygen mixture, response to comb pinching and SEPs returned either at the time of, or soon after, the onset of high frequency electrical activity in the suppressed EEG of broilers. The mean times to return of response to comb pinching and SEPs were 52 and 43 s, respectively. 7. Based on the time to onset of EEG suppression or loss of SEPs, exposure of broilers to either 90% argon in air, or a mixture of 30% carbon dioxide and 60% argon in air, resulted in quicker loss of consciousness than during exposure to a mixture of 40% carbon dioxide, 30% oxygen and 30% nitrogen. The time to return of consciousness after a 2 min exposure to the carbon dioxide-oxygen mixture was also found to be rapid.

Electrical stunning in commercial rabbits: Effective currents, spontaneous physical activity and reflex behaviour.

Electrical stunning was evaluated in commercial slaughter rabbits. Different voltage applications with varying current duration were tested in recovery experiments in 71 animals. Stunning parameters and duration of insensibility were measured and analysed for assessing stunning effectiveness. A minimum stunning current of 140 mA which can be achieved with application of 100 V was recommended.

Prevalence and duration of insensibility following electrical stunning in calves.

Sixty-one calves were electrically stunned with 100-250 V currents (103-1806 mA) and the prevalence and duration of insensibility was assessed from their physical behaviour, the presence of epileptiform activity in their electrocorticograms, and the absence of visual evoked responses in their electrocorticograms. A current applied at 100 V across the head for 3 s failed to induce insensibility in all cases. Currents at 150-250 V induced insensibility in all calves and the shortest duration of insensibility was 44 s. It is recommended that a 150-200 V current would be appropriate for commercial use.

Welfare of calves - 1. Investigations into some aspects of calf slaughter.

The relationship between carotid occlusion, systemic blood pressure and brain function following electrical stunning and exsanguination (sticking) in slaughter calves (< 10 weeks) was assessed. Electrocorticograms, systemic blood pressure and evoked responses were measured in the chloralose. anaesthetised and the unanaesthetised states. Electrical stunning produced relatively short periods of measurable epilepsy in slaughter calves (18 s average). The pattern of decline in blood pressure after sticking showed variations between animals. However, the results indicated that two groups of animals could be recognised: a carotid occlusion (ballooning group) and no carotid occlusion (non-ballooning) group. The animals with ballooning (six out of 15 = 40%) developed occlusions of the caudal severed ends of the carotid arteries. These swellings, the so-called 'ballooning' effect, were characterised by large clots forming plugs at the severed ends of the arteries. When this phenomenon occurred the haemorrhaging was clearly impeded. This was reflected in the blood pressure traces which showed recovery episodes coinciding with the occurrence of the carotid occlusions. Our study indicates that in the worst possible case the development of a restriction to the outflow of blood can delay the rate of haemorrhaging and the decline in blood pressure. This can lead in turn to sustained brain function as evidenced by the continued presence of evoked responses following stun recovery and a long time to onset of the isoelectrical state in the electrocorticogram.

Welfare of calves - 2. Increase in vertebral artery blood flow following exsanguination by neck sticking and evaluation of chest sticking as an alternative slaughter method.

The role of the vertebral arteries in delaying loss of sensibility following neck sticking in slaughter calves was investigated. Vertebral artery blood flow was measured using probes before, during and after electrical stunning and slaughter. Systemic blood pressure, electrocorticogram, visually evoked responses and the occurrence of carotid occlusions were also recorded. When carotid occlusion occurred, the time to onset of brain failure was delayed based on the development of an isoelectric state. In addition, when carotid occlusion occurred the mean arterial blood pressure was sustained for longer following slaughter, and concurrently vertebral artery blood flow could be maintained at about 30% of its initial level for up to 3 min. In some animals vertebral artery flow increased substantially following sticking. When chest sticking was used no occlusion of vessels occurred, mean arterial blood pressure fell promptly (within 8 s) and the onset of an isoelectric state did not extend beyond one minute. In addition, visually evoked responses were not present after 5 s following chest sticking.

The effectiveness of high frequency electrical stunning in pigs.

Two commercially-available high frequency electrical stunners producing either AC sinewaves (146 V; 1592 Hz) or DC squarewaves (162V; 1642 Hz) having different waveforms were tested for their effectiveness in stunning pigs and compared with conventional 50 Hz sinusoidal waveforms. Seventy-nine pigs were stunned using the highest voltage settings, allowed to recover, and the duration of insensibility was assessed from behavioural signs. It was found that the pigs were adequately stunned by this method even though some physical responses differed from 50 Hz stunning. An additional experiment was conducted on three pigs to examine whether the epileptic brain activity (indicative of unconsciousness) occurred following high frequency stunning and to assess the effects on visually evoked responses. It was confirmed that high frequency stunning produced epilepsy and unconsciousness and appeared therefore to be acceptable from an animal welfare standpoint. However, the average stunning to sticking intervals were shorter with high frequency stunning compared with 50 Hz stunning.

Pig slaughtering procedures: Head-to-back stunning.

High voltage head-to-back electrical stunning can induce vertebral compression fractures, blood splash and poor meat quality in pigs. This experiment was designed to determine the optimum position of the rear electrode which would not only stun and kill pork and bacon weight pigs with a 1·3 A 50 Hz sinewave but would also produce a good carcass with desirable meat quality. Although there was a trend for less breaks to occur the further forward the rear electrode was positioned, there was no position which gave 100% cardiac fibrillation and an absence of breaks. The incidence of blood splash, muscle haemorrhages and the variations in meat colour were not related to electrode position and fell in the 'normal' range quoted by other workers. The severity and incidence of kicking after stunning was reduced the more caudal the electrode position. This was in direct contrast to the effect on compression fractures where a reduction was seen with the more rostral applications.