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Biomedical subjects

N G Gregory

Publications and source records attributed to N G Gregory.

At least 19 recordsLinked to original sources
PubMed1992

Causes of trauma in broilers arriving dead at poultry processing plants.

A post mortem examination was made on 1324 broiler carcases which arrived dead after being transported to six processing plants. The carcases were dissected and evaluated for trauma and obvious cause of death. Of the birds sent to the plants on the day of collection 0.19 per cent arrived dead and 35 per cent of these were thought to have died as a result of trauma. Haemorrhage associated with dislocation of the femur at the hip was the most common cause of trauma. Ruptured livers and crushed heads were other important traumatic injuries.

Abattoirs↗
PubMed1992

Prevalence of leg weakness in broiler chickens and its relationship with genotype.

A method for measuring the prevalence of leg weakness by assessing the walking ability of broilers was developed. Walking ability was divided into six categories, from completely normal to immobile. The method was found to give consistent results when performed by the same people. In a survey of commercial, intensively reared broilers, 90 per cent had a detectable gait abnormality and 26 per cent suffered an abnormality of sufficient severity for their welfare to be considered compromised. The prevalence of leg weakness in free range broilers, and three commercial breeds of broilers was determined. The results indicated that genetic factors were an important cause of leg weakness in broilers and also identified a possible relationship between liveweight and leg weakness.

Animals↗
PubMed1992

Survival rate and carcase downgrading after the stunning of broilers with carbon dioxide-argon mixtures.

As chickens may rapidly regain consciousness after gas stunning, the effects of a two minute exposure to a carbon dioxide-argon mixture on survival rate were investigated. Broilers were stunned in batches of 10 per transport crate with a mixture of 10, 20 or 30 per cent carbon dioxide in argon with 5 per cent residual oxygen. The birds were exposed to the gaseous atmosphere for two minutes. A control group of birds was electrically stunned (120 mA for four seconds; 50Hz sinusoidal waveform). In addition, the incidence of carcase downgrading conditions after stunning with 20 per cent or 30 per cent carbon dioxide in argon with 5 per cent residual oxygen was compared with the incidence after electrical stunning. The results showed that stunning with 10 and 20 per cent carbon dioxide in argon with 5 per cent residual oxygen resulted in survival rates of 24 and 1 per cent, respectively. Stunning with 30 per cent carbon dioxide in argon with 5 per cent residual oxygen resulted in the death of all the broilers. Electrical stunning resulted in a significantly (P less than 0.001) larger number of broilers with breast muscle haemorrhaging and broken furculum and coracoid bones, whereas stunning with gas mixtures resulted in a significantly (P less than 0.001) higher incidence of broilers with damaged wing bones. Electrical stunning of broilers resulted in a significantly higher pH in the breast muscles 20 minutes post mortem than stunning with carbon dioxide-argon mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)

Abattoirs↗
PubMed1992

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.

Abattoirs↗
PubMed1992

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.

Abattoirs↗
PubMed1992

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.

Abattoirs↗
PubMed1991

Effect of slaughter by removal from water on visual evoked activity in the brain and reflex movement of rainbow trout (Oncorhynchus mykiss).

The effects of removal from water and death by anoxia on brain function and reflex movement were examined in conscious trout. Visual evoked responses (VERS) were measured in fish with a body temperature of 20 degrees C, 14 degrees C and 2 degrees C. On average the fish took 2.6 minutes at 20 degrees C, 3.0 minutes at 14 degrees C and 9.6 minutes at 2 degrees C to lose VERS, and 11.5, 27.7 and 197.6 minutes, respectively, to lose all movement. VERS were absent from fish anaesthetised with MS222. From a humanitarian standpoint these results indicate that fish killed by anoxia could be exposed to periods of distress or suffering, and that cooling them in ice prolongs this period.

Anesthesia↗
PubMed1991

Effect of husbandry system on broken bones and bone strength in hens.

The effects of rearing system, forced moulting and three different layer housing systems on broken bones and bone strength, were examined in hens at the end of lay. Weak bones and broken bones were more common in battery hens which had been reared to point of lay on deep litter rather than in cages. The incidence of old breaks was greater in perchery birds (14 per cent) than in tiered terrace birds (5 per cent), and there was also a difference between their incidence in two types of perchery design (17 per cent and 11 per cent). Moulting was associated with a transient decline in bone strength, followed by an increase in strength during the second lay.

Animal Husbandry↗
PubMed1991

Efficiency of bleeding of broilers after gaseous or electrical stunning.

The efficiency of bleeding of broilers (g blood/kg liveweight) was measured after stunning them with either 45 per cent carbon dioxide in air for two minutes or with 2 per cent oxygen (achieved by displacing air with argon) for two minutes or with an electric current (77 or 104 mA at 50 Hz for four seconds). The results indicated that the initial rate of bleeding was higher in the electrically stunned broilers with non-fibrillated hearts than in the gas stunned broilers and electrically stunned broilers with fibrillated hearts. This difference was significant up to 60 seconds after neck cutting (P less than 0.05) but after 140 seconds all the broilers had bled out to a similar extent (30 to 33 g/kg liveweight). It is concluded that after gas stunning the time interval between neck cutting and scalding should be 60 to 140 seconds.

Abattoirs↗
PubMed1991

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.

Animal Welfare↗
PubMed1991

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.

Animals↗
PubMed1991

Preferential feeding behaviour of hens in different gaseous atmospheres.

1. The object of this study was to identify the concentrations of carbon dioxide (CO2) and hypoxia (induced by argon) which hens could detect and by preference avoid. 2. Hens were housed in an apparatus consisting of an upper roosting chamber connected to two descending passages which led to separate identical feeding chambers. The gas concentration in both these feeding chambers could be regulated. 3. The hens were allowed to feed in either a normal air atmosphere or an altered atmosphere containing a sub-stunning concentration of CO2 or argon. The birds' preference for feeding in the two chambers was used as an indicator of the concentration which they chose to avoid. 4. The study involved two experiments. In the first it was found that when the concentration of CO2 was raised above 5%, or the concentration of oxygen was reduced to 10% or below, the occupancy of that chamber was significantly reduced. 5. The results of the second experiment confirmed that a concentration of above 7.5% CO2 or oxygen levels of 10% or below can be detectable to hens and, given a free choice, the hens learnt to avoid such atmospheres. 6. The presence of a dominant bird in the roosting chamber or in the feeding chamber containing air caused the subordinate birds to enter the treatment chamber containing gas. This would imply that the unpleasantness of the stunning gases at the concentrations used in this study was less severe than the social pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The role of electrical stunning, bleeding and plucking efficiency on the downgrading of chicken carcases.

This study examined the effects of inducing a cardiac arrest at electrical stunning, in combination with impaired bleeding and severe plucking, on the incidence of haemorrhages and broken bones in chicken carcases. It was concluded that with the possible exception of breast muscle haemorrhages none of the downgrading conditions were attributable solely to electrical stunning. Poor neck cutting, too severe plucking and flapping of the wings before death also played a part.

Abattoirs↗
PubMed1990

Comparison of neck dislocation and percussion of the head on visual evoked responses in the chicken's brain.

The effect of neck dislocation, by stretching or by crushing, on the ability of the chicken's brain to sustain visual evoked responses was compared with the effect of a percussive blow. Less than 10 per cent of the birds whose necks were dislocated showed signs of concussion. It was concluded that neck dislocation may not concuss chickens, and that it is therefore uncertain whether it induces instantaneous unconsciousness.

Animal Welfare↗
PubMed1990

An evaluation of the effectiveness of handheld stunners for stunning chickens.

Two experiments were conducted in which the spontaneous physical behaviour, spontaneous electroencephalogram (EEG) and somatosensory evoked potentials were examined in chickens stunned with a handheld, head-only stunner operating at 117 v. Thirteen of 14 birds lost their evoked potentials after stunning, and when they were exsanguinated within 15 seconds they did not regain them before they died. The remaining bird appeared to have evoked potentials after stunning but there was a movement artifact in its EEG and it is possible that they were not genuine responses. When head-only stunning was applied to 50 birds for one second the birds appeared to be stunned instantaneously, in terms of their spontaneous physical behaviour. However, they recovered more rapidly than 40 birds which were stunned for seven seconds. It was concluded that the handheld stunner can stun a bird effectively, and provided that the bird's neck is cut promptly, can kill it humanely.

Abattoirs↗