Comparison of recovery of sheep, goats, and calves from reversible electrical head-only and head-to-body stunning for halal meat production.

AIMS: To compare the recovery of lambs, goats, and calves from head-only (HO) or high-frequency head-to-body stunning and evaluate the complementary use of behaviour and electroencephalography (EEG) to assess return to consciousness after electrical stunning in these species. METHODS: Six-month-old lambs, adult goats and calves (< 7 days old) were subjected to reversible head-only stunning (50 Hz, 1 A, 2 seconds) or reversible high-frequency head-to-body stunning (RHTB: HO followed by 2,000 Hz, 2 A, 4-second stun to body). Following stunning, behavioural recovery was assessed in 21 lambs, 22 goats, and 20 calves. Latencies to first perform behaviours (end of convulsions, head lift, attempt to right, successful righting, attempt to stand, successful standing) after stunning were scored from video recordings. Recovery of electrical brain activity indicative of consciousness was assessed using EEG in a separate cohort of minimally-anaesthetised lambs, goats and calves (n = 20 per species). EEG traces collected before and after stunning were classified as normal, epileptiform, isoelectric, or transitional activity. Following stunning, the duration of epileptiform and isoelectric activity combined (states of brain activity incompatible with conscious awareness) was calculated, as was latency to return of normal (pre-stun) EEG. RESULTS: The RHTB stun was reversible in all three species, although one sheep failed to recover and was euthanised. Both methods caused tonic and clonic convulsions in all species. Behavioural recovery of sheep and calves was similar for both methods while goats took longer to recover from RHTB than HO stunning. There was no evidence of differences between methods in the duration of EEG incompatible with consciousness or the latency to recovery of normal EEG. CONCLUSIONS: Head-to-body stunning as applied here produced a reversible electrical stun in lambs, adult goats and young calves, although the benefits in terms of meat quality and operator safety are uncertain. Goats took longer to recover behaviourally from head-to-body stunning, possibly due to disrupted motor function, but there was no indication that post-stun unconsciousness lasted longer than following head-only stunning in any species. The normal behaviour for the animals' developmental age should be considered when deciding on behavioural indicators of recovery. The minimal anaesthesia model provided excellent quality EEG data that was valuable for interpretation of the behavioural responses. CLINICAL RELEVANCE: For the purposes of pre-slaughter stunning of sheep, goats and young calves, recovery appears comparable between the two methods, with all but 1/63 animals in the behaviour study recovering normal function.

Indicators of dehydration in healthy 4- to 5-day-old dairy calves deprived of feed and water for 24 hours.

Our objective was to identify practical indicators of calf dehydration that could be used in an industry context. Eleven healthy 4-d-old commercial dairy calves were fed 2 L of mixed colostrum, then deprived of food and water for 24 h. Total body water was determined in the fed state using the deuterium dilution method. Body weight, along with a range of behavioral and physiological variables, was recorded 1 h after feeding, then at 90-min intervals through to 24 h. Blood samples were collected at every second sampling to assess changes in plasma hemoglobin, hematocrit, and osmolality. Linear mixed-effects models were used to explore associations between hydration status (% body water) and outcome variables. All calves remained bright and alert with good suckling reflexes throughout the 24-h period. After 24 h, total body water had decreased by an average of 8.4% (standard error 1.18), consistent with mild to moderate dehydration. Skin tent return time, capillary refill time, and detectable enophthalmos were associated with hydration status. Calves with skin tent return times of 3 s or longer were 4.4 percentage points less hydrated than those with return times of less than 3 s. Similarly, a capillary refill time of 3 s or longer was associated with a 4.3 percentage point reduction in hydration compared with refill times of less than 3 s. Calves with detectable enophthalmos (≥1 mm) were 3.5 percentage points less hydrated than those without enophthalmos. The skin tent, capillary refill, and enophthalmos tests are all relatively simple to perform and, although requiring the calf to be briefly restrained, can easily be performed by a single operator. The outcome of these tests was relatively consistent, in that calves above the threshold in any test were 3.5 to 4.5% less hydrated than calves below the threshold. As such, these tests may be of practical utility to identify calves with mild to moderate dehydration in an industry setting.

Effects of Obesity on the Regulation of Macrophage Population in the Prostate Tumor Microenvironment.

Obesity is associated with a greater risk of prostate cancer mortality. However, the mechanisms connecting obesity to the progression of prostate cancer remain unknown. This study determined the impact of obesity on macrophage recruitment and tumor-associated macrophage (TAM) polarization in the prostate tumor microenvironment, since a high concentration of TAMs in tumors has been linked to progression in prostate cancer. We utilized an in vitro model in which pre-adipocytes, prostate cancer cells, and macrophages were exposed to sera from obese or nonobese men, or conditioned media generated under obese or nonobese conditions. Matrigel invasion chambers were used to assess macrophage recruitment in vitro, and immunohistochemical analysis evaluated recruitment in a PTEN knockout mouse model. qPCR was used to measure mRNA levels of CCL2, COX-2, IL-10, TGF-beta, VEGF-A, arginase-1, and MMP-9. PGE2 production was measured by ELISA. Obesity increased macrophage and TAM recruitment, and increased mRNA levels of TAM markers in macrophages. Similarly, obese conditions increased CCL2 and COX-2 expression, as well as PGE2 levels in prostate cancer cells. COX-2 inhibition resulted in lower expression of obesity-induced TAM markers. Our data suggest that obesity promotes macrophage infiltration into the prostate tumor microenvironment, and induces TAM polarization through the COX-2/PGE2 pathway.

Comparison of neural histomorphology in tail tips from pigs docked using clippers or cautery iron.

Tail docking of pigs is commonly performed to reduce the incidence of unwanted tail-biting behaviour. Two docking methods are commonly used: blunt trauma cutting (i.e. using side clippers), or cutting and concurrent cauterisation using a hot cautery iron. A potential consequence of tail amputation is the development of neuromas at the docking site. Neuromas have been linked to neuropathic pain, which can influence the longer-term welfare of affected individuals. To determine whether method of tail docking influences the extent of neuroma formation, 75 pigs were allocated to one of three treatments at birth: tail docked using clippers; tail docked using cautery iron; tail left intact. Tail docking was performed at 2 days of age and pigs were kept under conventional conditions until slaughter at 21 weeks of age. Tails were removed following slaughter and subjected to histological examination. Nerve histomorphology was scored according to the following scale: 1=discrete well-organised nerve bundles; 2=moderate neural proliferation and disorganisation affecting more than half of the circumference of the tail; 3=marked neural proliferation to form almost continuous disorganised bundles or non-continuous enlarged bundles compressing the surrounding connective tissue. Scores of 2 or 3 indicated neuroma formation. Scores were higher in docked pigs than undocked pigs (P<0.001), but did not differ between pigs docked using clippers and those docked using cautery (P=0.23). The results indicate that tail docking using either clippers or cautery results in neuroma formation, thus having the potential to affect long-term pig welfare.

Proton magnetic resonance spectroscopy and outcome in term neonates with chorioamnionitis.

OBJECTIVE: Evaluate brain metabolites, which reflect neuroinflammation, and relate to neurodevelopmental outcomes in healthy term neonates exposed to chorioamnionitis. STUDY DESIGN: Thirty-one healthy term neonates with documented fetal inflammatory response after maternal chorioamnionitis underwent magnetic resonance spectroscopy (MRS), with voxels placed in basal ganglia (BG) and frontal white matter. Bayley III examinations were performed at 12 months of age. RESULT: Infants with below average outcomes did not show the same increase in NAA/Cho ratios postnatally as the group with normal outcomes. Decreased NAA/Cho and increased Lac/Cr in BG correlated with lower motor and cognitive composite scores, respectively, controlling for postnatal age. In males, increased lactate/NAA in BG were associated with lower motor scores. Funisitis severity was associated with decreased NAA/Cho and increased mI/NAA in males. CONCLUSION: In healthy term newborns with chorioamnionitis, MRS ratios shortly after birth may provide evidence of occult neuroinflammation, which may be associated with worse performance on 1-year neurodevelopmental tests.

A scientific comment on the welfare of domesticated ruminants slaughtered without stunning.

This review provides a scientific comment on the welfare of ruminants slaughtered by ventral-neck incision without stunning. Evidence is derived from studies of calves, sheep and goats. Reference is also made to findings in other mammals including humans. Pain is an inherently subjective experience and only indirect indices are available in animals. Neurophysiological tools are widely used in humans to assess pain and have demonstrated that electroencephalographic (EEG) variables correlate well with subjective evaluations of pain. These neurophysiological tools have also been applied in animal studies. In humans pain is associated with major cutting injuries and it is widely accepted that farm animals also experience pain due to such injuries. Overwhelming international scientific opinion has long been that slaughter by neck incision of conscious animals causes pain. A series of studies in calves demonstrated that slaughter by ventral-neck incision is likely to be perceived as painful. It is proposed that, as in cattle, non-stunned sheep and goats would experience pain in a similar manner. The precise assessment of the point after slaughter at which non-stunned animals become insensible remains a major methodological challenge. In sheep it is at least 2-8 seconds, but may be 8-20 seconds in duration. In cattle the mean duration is similar, but can commonly be extended to longer than 60 seconds with occasional instances of even greater durations. Taken together, these findings indicate that because the slaughter of cattle, sheep and goats by ventral-neck incision without prior stunning is likely to cause pain, this poses a risk to animal welfare.

Spontaneous electroencephalographic changes in a castration model as an indicator of nociception: a comparison between donkeys and ponies.

REASONS FOR PERFORMING STUDY: Donkeys are believed to be less demonstrative of pain than ponies. Research into comparative sensory processing between these species is required to elucidate these behavioural differences. OBJECTIVES: To compare changes in the electroencephalogram (EEG) recorded during castration between donkeys and ponies. STUDY DESIGN: Prospective clinical study. METHODS: Six ponies and 6 donkeys were castrated under halothane anaesthesia after acepromazine premedication and thiopental anaesthetic induction. Markers were inserted into the EEG recording at the time of skin incision (skin) and emasculation (emasc) for both testicles (T1 and T2) during a closed castration. Raw EEG data were analysed and the EEG variables median frequency (F50 ), total power (Ptot ) and spectral edge frequency (F95 ) derived using standard techniques. Baseline values of F50 , Ptot and F95 for each animal were used to calculate the percentage change from baseline at T1skin, T2skin, T1emasc and T2emasc. RESULTS: Decreased F50 values relative to baseline were observed in 4 ponies and 2 donkeys across all castration time points. In the remaining animals, the F50 value increased compared with baseline. Both donkey and pony groups showed an overall decrease in Ptot values compared with baseline at T1skin, but the magnitude of the decrease was significantly less (P = 0.004) in ponies than in donkeys. Donkeys demonstrated an overall greater increase (P = 0.05) in F95 values at T1skin relative to baseline compared with ponies. CONCLUSIONS: Electroencephalographic responses to the noxious stimulus of castration were noted in both donkeys and ponies. Donkeys demonstrated a greater change in Ptot in response to castration than ponies; thus, donkeys appear to demonstrate a cerebral cortical response to a noxious stimulus that is similar to or greater than that in ponies, suggesting that their subtle behavioural expression of pain is not due to a difference in cortical processing of noxious sensory stimuli.

Electroencephalographic evaluation of decapitation of the anaesthetized rat.

The objective of this study was to evaluate the changes in electroencephalographic (EEG) power spectrum in response to decapitation of anaesthetized rats, in order to assess the nociception or otherwise of this procedure. Ten young adult male Sprague-Dawley rats were anaesthetized with halothane in oxygen and anaesthesia was maintained at a stable concentration of halothane between 1.20% and 1.25%. The rat's head and neck were placed through the opening of a small animal guillotine so that the blade of the guillotine was positioned over the atlanto-occipial joint of the rat's neck. The EEG was recorded in a five-electrode montage, bilaterally. After recording a 15 min baseline the rat was decapitated by swiftly pressing the guillotine blade and the EEG recording was continued until the signal was isoelectric on both channels. Changes in the median frequency (F50), 95% spectral edge frequency (F95) and total power of the EEG (Ptot) were used to investigate the effects of decapitation. During the first 15 s following decapitation, there were significant increases in the F50 and F95, and a decrease in the Ptot compared with baseline values. There was a clear window of time immediately following decapitation where changes in the EEG frequency spectrum were obvious; these changes in the EEG indices of nociception could be attributed as responses generated by the rat's cerebral cortex following decapitation.

Effects of tramadol or morphine in dogs undergoing castration on intra-operative electroencephalogram responses and post-operative pain.

AIM: To compare the effects of pre-operatively administered tramadol with those of morphine on electroencephalographic responses to surgery and post-operative pain in dogs undergoing castration. METHODS: Dogs undergoing castration were treated with either pre-operative morphine (0.5 mg/kg S/C, n = 8) or tramadol (3 mg/kg S/C, n = 8). All dogs also received 0.05 mg/kg acepromazine and 0.04 mg/kg atropine S/C in addition to the test analgesic. Anaesthesia was induced with thiopentone administered I/V to effect and maintained with halothane in oxygen. Respiratory rate, heart rate, end-tidal halothane tension (EtHal) and end-tidal CO2 tension (EtCO2) were monitored throughout surgery. Electroencephalograms (EEG) were recorded continuously using a three electrode montage. Median frequency (F50), total power (Ptot) and 95% spectral edge frequency (F95) derived from EEG power spectra recorded before skin incision (baseline) were compared with those recorded during ligation of the spermatic cords of both testicles. Post-operatively, pain was assessed after 1, 3, 6 and 9 h using the short form of the Glasgow composite measure pain scale (CMPS-SF). RESULTS: Dogs premedicated with tramadol had higher mean F50 (12.2 (SD 0.2) Hz) and lower Ptot (130.39 (SD 12.1) µv(2)) compared with those premedicated with morphine (11.5 (SD 0.2) Hz and 161.8 (SD 15.1) µv(2), respectively; p<0.05) during ligation of testicle 1. There were no differences in EEG responses between the two treatment groups during ligation of testicle 2 (p>0.05). The F95 of the EEG did not differ between the two groups during the ligation of either testicle (p > 0.05). Post-operatively, no significant differences in the CMPS-SF score were found between animals premedicated with tramadol and morphine at any time during the post-operative period. No dog required rescue analgesia. CONCLUSION AND CLINICAL RELEVANCE: Tramadol and morphine administered pre-operatively provided a similar degree of post-operative analgesia in male dogs at the doses tested.

Effects of tramadol, morphine or their combination in dogs undergoing ovariohysterectomy on peri-operative electroencephalographic responses and post-operative pain.

AIM: To compare the peri-operative electroencephalogram (EEG) responses and post-operative analgesic efficacy of pre-operative morphine or tramadol with a combination of low-dose pre-operative morphine and post-operative tramadol, in dogs undergoing ovariohysterectomy. METHODS: Dogs undergoing routine ovariohysterectomy were treated with either pre-operative morphine (0.5 mg/kg S/C, n=8), or tramadol (3 mg/kg S/C, n=8), or pre-operative low-dose morphine (0.1 mg/kg S/C) and post-operative tramadol (3 mg/kg I/V, n=8). All dogs received routine pre-anaesthetic medication, and anaesthesia was induced with I/V thiopentone to effect and maintained with halothane in oxygen. Respiratory rate, heart rate, end-tidal halothane tension (EtHal) and end-tidal CO2 tension (EtCO2) were monitored throughout surgery. The EEG was recorded continuously in a three electrode montage. Median frequency (F50), total power (Ptot) and 95% spectral edge frequency (F95) of the EEG power spectra were compared during different 100-second periods of surgery: prior to and during skin incision, ligation of each ovarian pedicle, ligation of uterine body and skin closure. Post-operatively, pain was assessed using the short form of the Glasgow composite measure pain scale (CMPS-SF). RESULTS: There was no difference in F50 or Ptot of the EEG between baseline and noxious surgical events within each treatment group, or between the three groups (p>0.05). The mean F95 was higher during the first three periods of surgery for dogs administered tramadol and low-dose morphine than those that received 0.5 mg/kg morphine (p=0.001). Dogs that received low-dose morphine and tramadol had lower CMPS-SF pain scores after ovariohysterectomy than those that received either tramadol or morphine alone (p=0.001). There was no difference in pain scores between dogs in the latter two groups. CONCLUSION AND CLINICAL RELEVANCE: Tramadol and morphine administered pre-operatively provided an equal degree of post-operative analgesia in dogs after ovariohysterectomy. A combination of pre-operative low-dose morphine and post-operative tramadol produced better post-operative analgesia than either drug administered alone pre-operatively. Administration of analgesics pre- and post-operatively could result in improved post-operative well-being of ovariohysterectomised dogs.

Preliminary investigation of somatosensory evoked potentials in equine headshaking.

The aim of this study was to develop a technique for recording electrical activity of the equine cerebral cortex following application of a noxious electrical stimulus to the maxillary branch of the trigeminal nerve in order to investigate trigeminal nerve neurophysiology in control and headshaking horses. Triphasic somatosensory evoked potentials (SEPs) were recorded using subcutaneous needle electrodes in four control and four headshaking horses under general anaesthesia. Dural electroencephalography electrodes were used to record SEPs in one further control and one further headshaking horse. Headshaking horses appeared to have decreased middle latency and inter-peak intervals following stimulation of the trigeminal nerve compared with control horses, supporting abnormal trigeminal nerve physiology in equine headshaking.

[The role of the voltage-dependent anion channels in the outer membrane of mitochondria in the regulation of cellular metabolism].

The role of the voltage-dependent anion channels (VDAC) harbored in the outer membrane of mitochondria in the regulation of cellular metabolism was investigated using an experimental model of ethanol toxicity in cultured hepatocytes. It was demonstrated that ethanol inhibits State 3 and uncoupled mitochondrial respirations, decreases the accessibility of mitochondrial adenylate kinase localized in the intermembrane space of mitochondria, and suppresses ureagenic respiration and synthesis of urea in cultured hepatocytes. Increasing the permeability of the outer mitochondrial membrane with closed VDAC with high concentrations of digitonin (> 80 microM), which creates pores in the membrane, allowing the alternative bypass of closed VDAC, and restores all reactions suppressed with ethanol. It is concluded that the effect of ethanol in hepatocytes leads to global loss of mitochondrial functions due to the closure of VDAC, which limits the free diffusion of metabolites into the intermembrane space of mitochondria. Our studies demonstrated that ethanol affects the main mitochondrial functions and revealed the role of VDAC channels in the outer mitochondrial membrane in the regulation of liver specific intracellular processes such as ureagenesis. The data obtained can be used for the development of pharmaceutical drugs that prevent the closure of VDAC in mitochondria of ethanol oxidizing liver, thus protecting liver tissue from the hepatotoxic action of alcohol.

[Effect of ethanol on synthesis of serine and exchange of methyl groups in hepatocytes by NMR spectroscopy].

The method of NMR spectroscopy was used to investigate the role of voltage-dependent anion channels in the outer mitochondrial membrane in the mechanism of ethanol hepatotoxicity using the synthesis of serine and exchange of methyl groups in hepatocytes metabolizing 13C-labeled glycine. Here we present and describe a methodological approach developed for the independent monitoring of the synthesis of serine in two intracellular compartments: the cytoplasm and mitochondria of intact hepatocytes, and quantification of different serine isotopomers synthesized in hepatocytes from 13C-labeled glycine. The data obtained indicate that the treatment of cells with ethanol as well as cysteamine (specific inhibitor of mitochondrial synthesis of serine) suppressed the level of mitochondria but not cytoplasmic serine isotopomers. It is concluded that the decrease in the production of mitochondrial serine isotopomers in hepatocytes exposed to ethanol can be caused not only by decreased permeability of the outer mitochondrial membrane due to the closure of voltage-dependent anion channels and suppression of the exchange of substrates of serine synthesis in mitochondria but also by the restoration of the cytoplasmic and/or mitochondrial pool of pyridine nucleotides (NADH) during the oxidation of ethanol. Our work reveals a new mechanism of action of ethanol (alcohol intoxication) in hepatocytes through the regulation of glycine metabolism and opens new possibilities in the treatment of alcohol poisoning.

Developmental changes in the electroencephalogram and responses to a noxious stimulus in anaesthetized tammar wallaby joeys (Macropus eugenii eugenii).

The tammar wallaby joey is born extremely immature and most of its neurological development occurs in the maternal pouch. It is not known at what in-pouch age functions such as conscious sensory perception commence. We determined the electroencephalographic (EEG) responses to noxious stimulation in lightly anaesthetized tammar wallaby joeys. Baseline median (F50) and spectral edge (F95) frequencies, total power (Ptot) and frequency spectra between 1 and 30 Hz of the EEG power spectrum were determined. Joeys aged less than 127 days showed little or no EEG activity. Prolonged periods of spontaneous EEG activity were present by 142 days. This activity increased, as did the power in all frequencies, while the duration of any intervening isoelectric periods decreased with increasing in-pouch age. EEG responses to a noxious stimulus (toe clamping) changed with increasing in-pouch age as there was no response from joeys aged 94-127 days (no EEG), a minimal decrease in the F50 in those aged between 142 and 181 days (P = 0.052) and a greater decrease in the F50 in those aged between 187 and 261 days (P < 0.001). The pattern of these changes, which presumably reflects anatomical and functional maturation of the cerebral cortex, is similar to, but develops more slowly than, that reported in the rat. The opening of the eyes and development of the pelage are discussed as markers of when brain development may be sufficient for joeys to consciously perceive noxious sensations including pain.

Influence of human development and predators on nest survival of tundra birds, Arctic Coastal Plain, Alaska.

Nest predation may influence population dynamics of birds on the Arctic Coastal Plain (ACP) of Alaska, USA. Anthropogenic development on the ACP is increasing, which may attract nest predators by providing artificial sources of food, perches, den sites, and nest sites. Enhanced populations or concentrations of human-subsidized predators may reduce nest survival for tundra-nesting birds. In this study, we tested the hypothesis that nest survival decreases in proximity to human infrastructure. We monitored 1257 nests of 13 shorebird species and 619 nests of four passerine species at seven sites on the ACP from 2002 to 2005. Study sites were chosen to represent a range of distances to infrastructure from 100 m to 80 km. We used Cox proportional hazards regression models to evaluate the effects of background (i.e., natural) factors and infrastructure on nest survival. We documented high spatial and temporal variability in nest survival, and site and year were both included in the best background model. We did not detect an effect of human infrastructure on nest survival for shorebirds as a group. In contrast, we found evidence that risk of predation for passerine nests increased within 5 km of infrastructure. This finding provides quantitative evidence of a relationship between infrastructure and nest survival for breeding passerines on the ACP. A posteriori finer-scale analyses (within oil field sites and individual species) suggested that Red and Red-necked Phalaropes combined (Phalaropus fulicarius, P. lobatus) had lower productivity closer to infrastructure and in areas with higher abundance of subsidized predators. However, we did not detect such a relationship between infrastructure and nest survival for Semipalmated and Pectoral Sandpipers (Calidris pusilla, C. melanotos), the two most abundant shorebirds. High variability in environmental conditions, nest survival, and predator numbers between sites and years may have contributed to these inconsistent results. We recommend targeted management actions to minimize anthropogenic effects and suggest new research needed on this issue as expanding development is planned for the ACP of Alaska. In particular, we recommend research on demography of key predators and their importance with respect to nest survival, and experimental studies that better address challenges posed by high natural variability.

A re-evaluation of the need to stun calves prior to slaughter by ventral-neck incision : an introductory review.

Commercial slaughter of farm livestock usually employs an extensive incision that severs the soft tissues of the neck including the major blood vessels supplying and draining the brain. It is intended to cause a catastrophic decrease in cerebral blood flow with rapid onset of unconsciousness or insensibility. The tissues of the neck are innervated with nociceptive nerve fibres and their transection will cause a barrage of sensory impulses. Consciousness, and therefore the ability of the animal to feel pain and experience distress after the incision, may persist for 60 seconds or longer in cattle. These observations suggest that livestock may experience pain and distress during the period before they become unconscious (insensible). Psychological shock and fear may also be associated with the extensive tissue damage and blood loss. Pre-incision stunning has been adopted as a precautionary measure to prevent suffering. However, the question remains: How intense and noxious are these experiences? Recent methodological developments related to quantitative analysis of the electroencephalogram (EEG) allow the experience of pain to be assessed more directly than has hitherto been possible. This methodology has now been applied to the question of the slaughter of calves by ventral-neck incision. The new information demonstrates clearly for the first time that the act of slaughter by ventral-neck incision is associated with noxious stimulation that would be expected to be perceived as painful in the period between the incision and loss of consciousness. These data provide further support for the value of stunning in preventing pain and distress in animals subjected to this procedure.

Components of electroencephalographic responses to slaughter in halothane - anaesthetised calves : effects of cutting neck tissues compared with major blood vessels.

AIM: To identify whether cutting neck tissues or cutting major blood vessels initiates the mechanisms responsible for electroencephalographic (EEG) responses to slaughter by ventral-neck incision without prior stunning in halothane-anaesthetised calves. METHODS: Calves were assigned to two groups, viz transection of neck tissues with intact blood circulation through the brain (n=10), or transection of the major blood vessels of the neck but not most other neck tissues (n=7). They were minimally anaesthetised with halothane, using an established anaesthesia protocol. The animals in the neck-tissue transection group had their carotid arteries and jugular veins exposed and cannulated proximal and distal to the proposed site of subsequent ventral-neck incision; this diverted blood flow through these vessels so that cerebral perfusion and drainage were preserved. In animals in the blood-vessel transection group, the carotid arteries and jugular veins were exposed bilaterally by surgical dissection. They were then transected without further damage to the remaining structures of the neck. Changes in the median frequency (F50), 95% spectral edge frequency (F95), total power of the EEG (Ptot), and arterial blood pressure were compared within each group before and after neck-tissue or blood-vessel transection, and between groups following treatments. RESULTS: Neck-tissue transection resulted in little overall change in the F50, an increase in the F95, and an initial increase in Ptot followed by a transient decrease and eventual return to pre-treatment values. There was between-animal variation in these EEG parameters. Transection of the major blood vessels of the neck resulted in a decrease in F50 in most animals; changes in F95 were highly variable, and there was a decrease in Ptot. CONCLUSIONS: The EEG responses seen following neck-tissue and blood-vessel transection were qualitatively distinct, and suggested that cutting neck tissues caused greater noxious sensory input than transection of only the major blood vessels of the neck. These observations support the conclusion that the EEG responses seen after ventral-neck incision in intact animals are primarily due to noxious stimulation as a result of incision of ventral-neck tissues and not mainly as a result of loss of blood flow through the brain.

Electroencephalographic responses of halothane - anaesthetised calves to slaughter by ventral-neck incision without prior stunning.

AIM: To investigate whether the electroencephalographic (EEG) responses to slaughter by ventral-neck incision without prior stunning may be perceived as painful in halothane-anaesthetised calves. METHODS: Fourteen Angus steers were minimally anaesthetised with halothane, using an established anaesthesia protocol. EEG indices were recorded bilaterally for 5 minutes prior to and 5 minutes following ventral-neck incision. A single incision was made in the ventral aspect of the neck, severing all tissues ventral to the vertebral column including the major blood vessels supplying and draining the head. Changes in the median frequency (F50), 95% spectral edge frequency (F95) and total power of the EEG (Ptot) were used to investigate the effects of ventral-neck incision. At the completion of the experiment, brains of calves were examined histologically. RESULTS: During the 30 seconds following ventral-neck incision, the F95 and Ptot showed significant changes (p<0.05) compared with pre-treatment values. The F50 increased significantly from recordings from the right side of the cranium. No gross or histological abnormalities were detected in the brains following slaughter. CONCLUSIONS: This study is the first investigation of the noxiousness of slaughter by ventral-neck incision, using EEG spectral analysis. It demonstrated that there is a period following slaughter where ventral-neck incision represents a noxious stimulus.

Electroencephalographic responses to concussive non-penetrative captive-bolt stunning in halothane - anaesthetised calves.

AIM: To investigate the electroencephalographic (EEG) and cardiovascular responses of halothane-anaesthetised calves to non-penetrative captive-bolt stunning. METHODS: Ten calves were minimally anaesthetised with halothane, using an established anaesthesia protocol. The EEG, blood pressure and electrocardiogram (ECG) were recorded before and after non-penetrative captive-bolt stunning. Visual inspection and alterations in the total power of the EEG (Ptot) were used to investigate the effects of stunning. RESULTS: Captive-bolt stunning significantly altered cerebrocortical function in all animals. In four animals, Ptot decreased immediately following stunning and remained low throughout the recording period. In another five animals, Ptot responded to stunning in a biphasic manner characterised by an immediate decrease followed by a transient increase and then a final decrease to values similar to those of the non-biphasic animals. CONCLUSIONS: Non-penetrative captive-bolt stunning significantly altered cerebrocortical function in halothane-anaesthetised calves. The changes in cerebrocortical function would be sufficient to produce insensibility within 0 to 14 seconds in conscious animals.

Amelioration of electroencephalographic responses to slaughter by non-penetrative captive-bolt stunning after ventral-neck incision in halothane - anaesthetised calves.

AIM: To investigate the ability of non-penetrative captive-bolt stunning delivered after ventral-neck incision to ameliorate responses to noxious stimulation associated with slaughter by ventral-neck incision in halothane-anaesthetised calves. METHODS: Seven calves were minimally anaesthetised with halothane, using an established anaesthesia protocol. Electroencephalographic (EEG) indices of cerebrocortical activity were measured in response to ventral-neck incision followed 5 seconds later by non-penetrative captive-bolt stunning. Changes in heart rate and arterial blood pressure were measured and instances of occlusion of the carotid arteries were also noted. RESULTS: After ventral-neck incision there were periods of an active EEG in some calves, which ceased after non-penetrative captive-bolt stunning in most of the animals. Two calves had periods of active EEG following stunning. Arterial blood pressure decreased significantly after neck incision in all calves, including three with occlusion of the carotid arteries. CONCLUSIONS: Non-penetrative captive-bolt stunning after ventral-neck incision resulted in the cessation of functional cortical activity in the majority of calves. This procedure prevented the development of cerebrocortical responses to ventral-neck incision, demonstrated elsewhere, which would be painful in conscious animals subjected to this procedure. In addition, instances of carotid arterial occlusion had no significant effect on the decrease in arterial blood pressure.