Biomedical subjects
Publications and source records attributed to N G Gregory.
In a strain of Pietrain the distance between the vulva and the urethral meatus is greater than that of other breeds of pig. This difference is such that it is difficult to catheterise the bladders of Pietrain gilts since the available specula are either too short in length or too wide in diameter.
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Explore the source record for details and available documents.
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The spontaneous EEG and somatosensory evoked potentials (SEPs) were examined in chickens before and after electrical stunning using a waterbath stunner. Fifty-four per cent of the birds became epileptic and lost their SEPs, and 17% were non-epileptic and appeared to retain their SEPs. It was concluded that there was a reasonably close association between the presence of epileptiform activity in the EEG and the absence of SEPs following electrical stunning, but that the absence of SEPs could be preferred as an indicator of an effective stun on conceptual grounds.
This study examined the time to loss of consciousness in hens during stunning in argon-induced anoxia. Somatosensory evoked potentials (SEPs) and the spontaneous electroencephalogram (EEG) were recorded in 12 culled hens prior to and during stunning in less than 2% oxygen (air displaced by argon). An additional 20 hens were stunned with a similar concentration of oxygen and the time to loss of posture, eye closure, and the onset and duration of clonic and tonic convulsions were recorded. A further 10 hens were immersed in less than 2% oxygen for 15-17 s and their response to comb pinching was tested as soon as they had been transferred to atmospheric air. It is concluded that the birds had not lost the primary response in their SEPs by the time they started convulsing, but the reduction in the amplitude of the SEPs, changes in their spontaneous EEG and a negative response to comb pinch before the start of the convulsions indicated that the birds were unconscious when they convulsed.
The effects of head only or waterbath electrical stunning on somatosensory evoked responses in the brain of turkeys were examined. When head only stunning with a sinusoidal AC of 50 Hz was followed within 15 s by neck cutting the evoked responses were absent following the stun. When neck cutting was not performed, the evoked responses returned from 30 s after the stun. When currents between 120 and 250 mA were used in a waterbath stunner some birds retained their evoked responses immediately after the current was applied. The proportion of birds that retained their responses after the stun was not related to the level of the current that was applied.
The effect of stunning current frequency on the incidence of ventricular fibrillation was determined in broilers and hens. When a pulsed unipolar square wave (DC) was used the incidence of ventricular fibrillation decreased as the frequency was increased beyond 125 Hz. When a sinusoidal AC was used, 50 Hz killed some of the birds whereas at the corresponding r.m.s. currents no birds experienced a ventricular fibrillation with 1500 Hz. In quail, it was found that between 45 and 110 mA (50 Hz) all birds experienced a ventricular fibrillation. The effect of 50, 200 and 350 Hz square wave DC on carcass downgrading was examined in broilers, and there were no differences between the groups. It was concluded that there were few advantages from using high frequency stunning currents in poultry.
A previous investigation indicated that when hens were exposed to 2% oxygen in argon (anoxia) EEG suppression and loss of SEPs occurred at 17 and 29 s after exposure. In this study, hens were exposed to 49% carbon dioxide in air (hypercapnic hypoxia) or 31% carbon dioxide with 2% oxygen in argon (hypercapnic anoxia) and their spontaneous electroencephalogram (EEG) and somatosensory evoked potentials (SEPs) were investigated. The results indicated that EEG suppression and loss of SEPs occurred in 11 and 26 s, respectively, in hypercapnic hypoxia. These events occurred at 11 and 19 s, respectively, after exposure to hypercapnic anoxia. These results indicated that, with regard to preslaughter stunning/killing of chickens, a mixture of 31% carbon dioxide with 2% oxygen in argon resulted in a more rapid loss of evoked responses in the brain when compared with 49% carbon dioxide in air or with 2% oxygen in argon. It is concluded that stunning chickens with low concentrations of carbon dioxide in argon would result in a more rapid loss of consciousness.
The effect of using a non-steroidal anti-inflammatory analgesic (ketoprofen) on the plasma cortisol response in calves dehorned with or without regional analgesia was determined. One hundred calves divided into 10 groups, four control and six dehorned, were used. Blood samples were taken before and after dehorning and plasma cortisol concentrations were measured. Dehorning caused a marked rise in plasma cortisol concentrations which returned to pretreatment levels after seven hours. The animals given ketoprofen before dehorning had a cortisol response similar to the dehorned animals for the first 1.3 hours after dehorning but then the plasma cortisol concentration returned to pretreatment levels. When animals were given a regional analgesic and ketoprofen the plasma cortisol concentrations were similar to control animals which had not been dehorned, with a small increase in plasma cortisol concentrations for the first hour after dehorning and then a rapid return to pretreatment values. This response was significantly lower than that seen in calves which received only regional analgesia. The results of this study suggest that a systemic analgesic should be combined with regional analgesia if the distress associated with dehorning is to be abolished.