Regulation of bone mineral density in the grey squirrel, Sciurus carolinensis: Bioavailability of calcium oxalate, and implications for bark stripping.

The damage caused when grey squirrels strip the outer bark off trees and ingest the underlying phloem can result in reduced timber quality or tree death. This is extremely costly to the UK forestry industry and can alter woodland composition, hampering conservation efforts. The calcium hypothesis proposes that grey squirrels ingest phloem to ameliorate a seasonal calcium deficiency. Calcium in the phloem predominantly takes the form of calcium oxalate (CaOx), however not all mammals can utilise CaOx as a source of calcium. Here, we present the results of a small-scale study to determine the extent to which grey squirrels can utilise CaOx. One of three custom-made diets containing calcium in varying forms and quantities (CaOx diet, Low-calcium carbonate (CaCO3 ) diet and Control diet) were fed to three treatment groups of six squirrels for 8 weeks. Bone densitometric properties were measured at the end of this time using peripheral quantitative computed tomography and micro-computed tomography. Pyridinoline-a serum marker of bone resorption-was measured regularly throughout the study. Bone mineral density and cortical mineralisation were lower in squirrels fed the CaOx diet compared to the Control group but similar to that of those on the Low-calcium diet, suggesting that calcium from calcium oxalate was not effectively utilised to maintain bone mineralisation. Whilst no differences were observed in serum pyridinoline levels between individuals on different diets, females had on average higher levels than males throughout the study. Future work should seek to determine if this apparent lack of ability to utilise CaOx is common to a large sample of grey squirrels and if so, whether it is consistent across all areas and seasons.

Assessment of the effectiveness of head only and back-of-the-head electrical stunning of chickens.

The study assesses the effectiveness of reversible head-only and back-of-the-head electrical stunning of chickens using 130-950 mA per bird at 50 Hz AC. Three trials were conducted to compare both stunning systems: (a) behavioural assessment of return of consciousness, (b) insensibility to thermal pain, and (c) assessment of return of brain activity with visually evoked potentials (VEPs). Assessment of behaviour suggested that the period of unconsciousness following head-only electrical stunning was shorter in hens compared to broilers. Stunning across the back-of-the-head delayed the time to return of brainstem function compared to stunning with standard head-only electrodes. Additionally, back-of-the-head stunning produced a more prolonged period of electroanalgesia compared to head-only. Based on examination of return of brain function with VEPs in hens, back-of-the-head stunning produced a shorter-lasting stun than standard head-only. However, even for standard head-only, the stun was notably shorter than previously reported. In some birds, brain function had returned within 9 s after the end of stunning. The results suggest that some birds may recover consciousness prior to or during the neck cut. Based on these findings, back-of-the-head stunning and standard head-only stunning of hens should not be recommended without further development.

Blood in the respiratory tract during slaughter with and without stunning in cattle.

Bovine respiratory tracts were examined for blood following shechita without stunning, halal slaughter without stunning, and captive bolt stunning with sticking. In all three methods the cattle were in the upright (standing) position at the start of bleeding. Those that had not been stunned continued to breathe during the early part of bleeding whilst those that were stunned were not breathing. Nineteen percent of the shechita, 58% of the halal and 21% of the stunned plus stuck cattle had blood lining the inner aspect of the trachea. Thirty six percent, 69% and 31% had blood in the upper bronchi, respectively. Ten percent, 19% and 0% had fine bright red blood-tinged foam in the trachea, respectively. It was concluded that concerns about suffering from airway irritation by blood could apply in animals that are either not stunned before slaughter or do not lose consciousness rapidly whilst blood is present in the respiratory tract.

Effectiveness of poll stunning water buffalo with captive bolt guns.

Practical experience has indicated that shooting water buffalo with a captive bolt gun in the front of the head does not always produce an effective stun. Slaughtermen have been claiming that the poll position is more reliable, but under present EU regulations this shooting position is not allowed for domesticated bovines. This study examined the effectiveness of shooting water buffalo with captive bolt guns in the poll region. The depth of concussion was assessed in 30 water buffalo from physical collapse, presence or absence of corneal and palpebral reflexes, normal rhythmic breathing, eyeball rotation, nystagmus and whether the animal was re-shot. All except one animal collapsed immediately. The one animal that failed to collapse was not breathing. The prevalence of a shallow depth of concussion in the poll shot animals was 53%. Two had been shot through the spinal cord, and with the exception of those plus one other in which the bolt did not penetrate the brain, the other animals were considered to be adequately stunned. Post mortem examination of the brain showed that 79% of the under thirty month old animals were shot in the midbrain or brain stem, but these regions had to be avoided in over thirty month old animals because of the risk of damaging the brain stem sample needed for BSE testing. In addition, three water buffalo were shot in the crown position and one in the front of the head. The frontal position was ineffective as the animal did not collapse, and all animals shot in the crown position resumed breathing shortly after shooting, indicating a shallow depth of concussion. It is concluded that poll shooting can be effective in water buffalo, but it produces a shallow depth of concussion compared with frontal shooting in cattle. It requires accurate placement of the gun to ensure that buffalo are not shot through the spinal cord instead of the brain. Vigilance is needed in ensuring that the animals are stuck promptly so that none recover consciousness.

Animal welfare at markets and during transport and slaughter.

This review highlights some recent developments in our understanding of stress and physical injuries that occur before and during transport to slaughter, during handling at livestock markets, and at the time animals are put-up for slaughter within abattoirs. Stress in pigs during transfer to the stunning point within the abattoir has important effects on meat quality, and there is growing evidence that strenuous exercise or CO(2) stunning can contribute to oxidative rancidity in pigs, poultry and fish. In the EU, putting cattle through a crush in order to check that their eartag numbers correspond to their passport numbers is imposing additional stress, and there are reports that it is leading to greater hide contamination with Escherichia coli O157. Recent developments in stunning and slaughter include a better understanding of the causes of variation in captive bolt gun performance, the effectiveness of poll instead of frontal shooting in water buffalo, the prevalence of false aneurysms in carotid arteries during shechita and halal slaughter, and the stress effects of CO(2) stunning in fish. Stunning pigs with 90% CO(2) leads to less PSE meat than 80% CO(2). There have been concerns about the physical activity that cattle show following electrical stunning with an electrically induced cardiac arrest, and with electrical stunning using DC waveforms in broiler chickens. There is also growing concern about the hygiene problems that exist in wet markets, where animals are slaughtered alongside meat that is on display to customers.

Prevalence of ballooning of the severed carotid arteries at slaughter in cattle, calves and sheep.

Previous work in calves indicated that ballooning of the severed arteries is a potential concern in animals receiving a reversible stun before slaughter, and in animals not stunned before slaughter, as it could extend the duration of brain function before the animals die. This study determined the prevalence of ballooning of the carotid arteries in a total of 987 cattle, calves and lambs at slaughter. The severed ends of the carotid arteries were examined by palpation. The prevalence of ballooning that was 3cm or more in diameter, was 16%, 25% and 0% for cattle, calves and lambs, respectively. Artery sections were taken from a sample of large cattle and examined histologically. In ballooned arteries there was coagulated blood between the outer surface of the artery and the inner aspect of the connective tissue sheath surrounding the artery, suggesting the formation of a false aneurysm in the ballooning phenomenon.

A note comparing the welfare of Zebu cattle following three stunning-slaughter methods.

The objective of this study was to assess welfare of cattle during bleeding after slaughter with or without stunning. A total of 434 bulls were distributed across three slaughter treatments: penetrating captive bolt stunning followed by chest sticking (PCB, N=279), non-penetrating captive bolt stunning followed by halal slaughter (NPCB, N=67) and shechita without previous stunning (SHE, N=88). Four measures of possible consciousness and return to sensibility were recorded 20 and 60 s after bleeding as welfare indicators. They were the frequencies of responses to nostril stimulation and tongue pinch, spontaneous eye blinking, and rhythmic breathing. All responses were absent in stunned cattle at both 20 and 60 s, and in SHE cattle 7, 4, 10, and 100% of the animals presented these responses, respectively. Repeat shots were required for 46% NPCB and 2% PCB (P<0.05). The application of religious slaughter without previous stunning may result in greater risk of cattle suffering, pain and distress at slaughter.

Recent concerns about stunning and slaughter.

This review summarises information that is relevant to concerns that have recently been expressed about stunning and slaughter. It is known that captive bolt stunning can result in brain material passing to the lungs via the jugular veins. If future studies show that BSE prions pass beyond the lungs to the edible carcass, there will be a move away from captive bolt stunning in large cattle towards electrical stunning. Greater use of electrical stunning in large cattle will increase the importance of blood splash in the beef industry. The theoretical causes of blood splash are reviewed to improve our understanding of this problem. In some situations it can be due to excessive venous pressure causing rupture of a capillary bed some distance from the source of the pressure rise, but it is not known whether this applies to electrical stunning. Gas stunning is replacing electrical stunning for poultry because it can reduce blood spots, which is a similar condition to blood splash. Several gas stunning methods are now being used, but it is not clear which of these is the most humane. Anoxic stunning leads to carcass convulsions and this causes more carcass damage. In fish, recent developments in electrical stunning are showing promise in overcoming problems with carcass damage. It is recommended that rock lobsters should be chilled or frozen before butchery, to ensure a humane death.

The effects of depriving feed to facilitate transport and slaughter in sheep--a case study of cull ewes held off pasture for different periods.

AIM: To determine the ability of sheep to mobilise their body reserves after being deprived of feed prior to transport for slaughter. METHODS: A total of 240 3- and 4-year-old cull ewes were held off pasture for 0, 9, 18 or 30 hours (n=60 per group) then transported 1 hour by road, unloaded and washed, held in lairage for 3 hours then slaughtered. Blood samples were collected from a subsample of 60 unfasted ewes 1 week earlier, and from all ewes at exsanguination to determine concentrations of serum metabolites indicative of adaptation to fasting. In addition, several attributes of carcass quality were measured. RESULTS: At slaughter, increased time off pasture prior to transport resulted in no change in glucose concentrations in serum (p=0.140). There were differences (p<0.001) between the group fasted for 30 compared with 0 hours in mean concentrations of free fatty acids (0.98 (SD 0.32) vs. 0.58 (SD 0.23) mmol/L), ß-hydroxybutyrate (0.69 (SD 0.17) vs. 0.42 (SD 0.11) mmol/L), triglycerides (0.29 (min 0.13, max 0.83) vs. 0.22 (min 0.06, max 0.96) mmol/L) and urea (10.17 (SD 1.80) vs. 6.94 (SD 2.03) mmol/L). Different periods of feed deprivation had no effect (p>0.05) on carcass weights (mean 22.7, min 13.2, max 32.9 kg) or dressing out percentages (mean 40.9, min 27, max 49%). Meat ultimate pH was unaffected (p>0.05) by the period of feed deprivation but meat became darker (p<0.05) and had reduced redness (p<0.001) with increasing time off feed. CONCLUSIONS: The results suggest that sheep in variable body condition adapted to the periods of feed deprivation by mobilising their energy reserves without any evidence of metabolic depletion (e.g. depleted blood glucose or high meat pH). However, being deprived of feed they probably experience a degree of hunger.

Effect of a 350 Hz DC stunning current on evoked responses in the chicken's brain.

Somatosensory evoked responses in the chicken's brain were examined before and after stunning with a 350 Hz pulsed DC. When the current was greater than 120 mA, 93 per cent of the birds lost their evoked responses for at least 60 seconds. On this basis 120 mA per bird is recommended as an acceptable current for commercial use.

Effect of depth of immersion in the waterbath on the effectiveness of electrical stunning in chickens.

Broiler chickens were electrically stunned either by immersing their heads, necks and upper breast in a waterbath stunner or by immersing their heads only. The time to recovery of muscular activity was assessed, and it was found that the deeper immersion was associated with a slightly (10 second) shorter time to resumption of head righting. When hens which had previously been implanted with electroencephalogram electrodes were electrically stunned it was found that the incidence of somatosensory evoked responses during the first 60 seconds after applying the current was not influenced by the depth of immersion. It was concluded that depth of immersion had little influence on the effectiveness of electrical stunning.

Turkey slaughtering procedures: time to loss of brain responsiveness after exsanguination or cardiac arrest.

The effect of inducing a cardiac arrest or severing both carotid arteries on the spontaneous and visual evoked electrical activity in the brain were examined in anaesthetised turkeys. The time to loss of evoked activity was greater following the cardiac arrest. It was concluded that the potential humanitarian advantages of inducing a cardiac arrest at stunning are less pronounced in the turkey than for other poultry species.

Pig slaughtering procedures: time to loss of brain responsiveness after exsanguination of cardiac arrest.

The time taken for a conventional chest stick to produce the loss of flash-evoked responsiveness in the electrocorticogram of anaesthetised pigs was compared with a method involving fibrillation of the heart. On average severing the brachiocephalic trunk and anterior vena cava took 18 seconds to induce a loss of brain responsiveness, and inducing cardiac fibrillation took 19 seconds. It is concluded that a pig slaughtering method that stuns the brain and at the same time fibrillates the heart is likely to be more humane than the conventional slaughtering methods where there is a delay between the stunning and sticking operations.

Effect of fasting on capillary blood flow in sheep.

Capillary blood flow rate was measured in 29 tissues in two hourly fed and 26 hour fasted Blackface and Clun lambs using the radiolabelled microsphere technique. Blood flow declined with fasting in alimentary tract, skin of the ear and some of the larger skeletal muscles. It was concluded that capillary perfusion in nerve tissue was not affected by fasting whereas tissues principally responsible for energy absorption, expenditure and retention can experience a fall in capillary blood flow during fasting.

Effect of wetting a chicken's feathers on the effectiveness of electrical stunning.

Chickens were electrically stunned either when their bodies and feathers were wet or when they were dry. The time to recovery of muscular activity following stunning with 81 mA was assessed, and it was found that it was quicker in the wet birds. When hens which had previously been implanted with electroencephalogram electrodes were stunned with 119 mA it was found that the prevalence of somatosensory evoked responses during the first 60 seconds after applying the current was not significantly influenced by the wetness of the birds. It was concluded that electrical stunning with low currents in wet birds leads to a lower prevalence of ventricular fibrillation at stunning and a shorter lasting stun in the non-fibrillated birds. This effect is possibly due to some of the current tracking over the bird's wet body rather than through the brain.

Effect of incomplete immersion of the head in waterbath stunners on the effectiveness of electrical stunning in ducks.

Ten ducks were subjected to electrical stunning with their heads completely immersed in the water of a waterbath, and 10 ducks received the same current while only the bill and skin over the crop made contact with the water. The effect on visual evoked responses in the brain was examined. A higher proportion of birds had lost their visual evoked responses immediately following the current with whole head immersion. It is suggested that crop and bill immersion is less effective in disturbing brain function than whole head immersion.

Inhalation of water during electrical stunning in chickens.

Twenty live hens were subjected to electrical stunning using a waterbath containing a solution of technetium99 (99Tc), and 12 hen carcases were injected intratracheally with different doses of the same solution. The respiratory tract was dissected from the carcases and samples were assessed for the presence of radioactivity. Thirty-five per cent of the electrically stunned birds had 99Tc in their tracheas and 15 per cent had 99Tc in the lungs. From the dose response study it was estimated that the birds with radioactivity in their lungs had inhaled between 0.5 and 1 ml of water. In commercial slaughterlines this may be a hazard to meat hygiene.

Studies on the central nervous system: visually evoked cortical responses in sheep.

Several factors which were thought to affect the magnitude of flash evoked cortical potentials were examined in halothane-anaesthetised sheep. The proximity of the electrodes to the cortex and the patency of the eye which was contralateral to the recording electrodes had the greatest effect on the excursion distance of the visually evoked response. The choice of upper frequency filter (70 vs 700 Hz), the patency of the ipsilateral eye and closure of both eyelids resulted in relatively smaller reductions in excursion distance of the response. The importance of these findings in studies using evoked potentials for assessing sensibility and brain death in animals is discussed.

Time to loss of brain responsiveness following exsanguination in calves.

In the anaesthetised calf the time to loss of visually evoked cortical responsiveness after cutting the common carotid arteries and the jugular veins was 17 seconds. An earlier study showed that the corresponding interval for sheep was 14 seconds. In contrast to suggestions made by other workers, it is concluded that the time necessary for sticking at slaughter to induce brain dysfunction is similar in the two species.

Adipose tissue capillary blood flow in relation to fatness in sheep.

Capillary blood flow rate was measured in eight fat depots in eight Blackface and eight Clun lambs using the radiolabelled microsphere technique. Adipose tissue flow ranged from 3 to 47 ml 100 g-1 min-1 depending upon depot and degree of fatness. Blood flow declined with increasing fatness suggesting that perfusion was not an important constraint on the growth of fat. Blood flow rates were also measured in the fed and 26 hour fasted states but no effect from fasting was observed.