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Biomedical subjects

J C Newhook

Publications and source records attributed to J C Newhook.

14 recordsLinked to original sources
PubMed1987

Slaughter methods: electroencephalographic (EEG) studies on spinal cord section, decapitation and gross trauma of the brain in lambs.

By means of electroencephalograms (EEG), attempts were made to determine when insensibility could be presumed in five lambs, two subjected to immobilisation by the punctilla method, two decapitated and one shot by a captive bolt in the poll region. Section of approximately 80% of the spinal cord by the punctilla method had no apparent effect on sensibility and the technique was considered to be inhumane. The EEG obtained from a decapitated bead showed no obvious change in pattern for eight seconds and subsequent changes were similar to those associated with exsanguination only. Thus no evidence was obtained to indicate that decapitation causes immediate insensibility, neither was the belief substantiated that severance of the spinal cord, during the slaughter of sheep, hastens the onset of insensibility. These results also provide additional evidence on the inhumane nature of punctilla slaughter of cattle. The animal shot with a captive bolt in the poll region, as opposed to the frontal region, showed EEG activity for 78 seconds.

Journal Article↗
PubMed1981

Insensibility during slaughter of pigs in comparison to other domestic stock.

The onset of insensibility during slaughter was studied in five, 31-day-old pigs. The state of sensibility was determined from the study of electroencephalograms (EEC) which were of a bipolar transhemispheric derivation. In 3 pigs slaughtered by bilateral severance of both common carotid arteries and jugular veins, it was judged that insensibility occurred within 25 s and there was no resurgence of cerebrocortical activity following subsequent respiratory gasps. The EEGs became isoelectric within 115 s. These results are compared with previous findings by the authors that adult sheep and lambs slaughtered by similar techniques became insensible within 7 s whereas, in calves, the onset of insensibility was delayed for up to 85 s and there were resurgences of cerebrocortical activity, following a respiratory gasp, for more than 300 s. These differences in the apparent onset of insensibility in the 3 species of animal are discussed in relation to the anatomical features and possible dynamics of the blood supply to the brain during slaughter. It is concluded that for humane reasons, head-to-back electrical stunning of pigs is preferable to a head-only method.

Abattoirs↗
PubMed1976

Effects of different slaughter methods on bleeding sheep.

One hundred and sixteen sheep were slaughtered by five different methods in an attempt to determine the most practical technique which would result in rapid exsanguination without incision of the oesophagus. Techniques which involve stunning prior to slaughter were compared with the traditional New Zealand method by which fully conscious sheep are slaughtered by almost simultaneous severance of the major blood vessels of the neck and the spinal cord at the occipito-atlantal junction. Total amounts of blood lost and rates of bleeding were compared.

Abattoirs↗
PubMed1976

Cineradiography of the reticular groove mechanism.

The use of cineradiographic studies in the interpretation of how sucked liquid passes to the abomasum in young sucking ruminants is described with special reference to experimental studies in lambs and calves. The work involved an examination of the movements of stainless steel wire or clips inserted via a gastrostomy into the mucosa of the caudal thoracic oesophagus, lips of the reticular groove and margins of the reticulo-omasal orifice. This assisted the interpretation of how these structures are involved in the passage into the abomasum of sucked liquid and into the reticulo-rumen of liquid or solid ingesta or saliva swallowed independently of sucking. An understanding of contributions made by the oesophagus, reticular groove and reticulo-omasal orifice to the passage of sucked liquid into the abomasum was aided by the use of the autonomic blocking agents, atropine and hexamethonium.

Abomasum↗
PubMed1975

Scanning electron microscope study of bacteria associated with the rumen epithelium of sheep.

Examination of the rumen epithelium of sheep by scanning electron microscopy revealed bacteria associated with the epithelial surface. Comparison of epithelial surfaces from 10 sheep revealed areas that were consistently densely covered with bacteria and other areas where the cover was consistently light. The bacterial populations were frequently of mixed morphological types, but areas populated with a single type were also observed. This finding, together with the discovery of bacterial forms not previously described in rumen contents, suggests that a specific flora may exist on the rumen epithelial surface. The functional significance of such a population is discussed.

Animals↗
PubMed1974

Effects of vagotomy, atropine, hexamethonium and adrenaline on the destination in the stomach of liquids sucked by milk-fed lambs and calves.

1. The normal passage to the abomasum of liquid sucked by lambs and calves was confirmed in radiographic studies to be changed to passage of liquid to the reticulum and rumen after cervical or abdominal vagotomy.2. The effects of hexamethonium (8-10 mg kg(-1) I.V.) were similar to those of vagotomy.3. Atropine (200-800 mug kg(-1) I.V.) had either no detectable effect on the destination in the stomach of liquid sucked by lambs or caused a partial failure of the reticular groove mechanism.4. Fluid sucked by lambs passed wholly to the abomasum after adrenaline (5-40 mug kg(-1) I.V.).5. Atropine and adrenaline caused a greater dysfunction of the reticular groove mechanisms in calves than in lambs.6. Contraction of the reticular groove was observed via rumen fistulae in three lambs. Eversion of the caudal oesophagus into the reticulum which occurred when saliva was swallowed into the reticulum and rumen was not observed when liquids were sucked from a bottle.7. The continued passage to the abomasum of sucked liquid in atropinized lambs has been taken as an indication of the importance of caudal oesophageal reactions, tonic activity of the reticular groove and the atropine-resistant vagally induced opening of the reticulo-omasal orifice in the reticular groove mechanism.

Abomasum↗
PubMed1972

Effects of stimulation of efferent fibres of the vagus on the reticulo-omasal orifice of the sheep.

1. The reticulo-omasal orifice has been observed and its activity recorded in decerebrate and spinal preparations of lambs and in lambs and sheep anaesthetized with chloralose.2. Spontaneous closure movements at about 6/min were seen, or recorded from balloons placed in the orifice in all types of preparation when both vagus nerves had been cut and after atropine, hexamethonium, phentolamine and propranolol had been given I.V.3. The effects on the reticulo-omasal orifice of stimulation in the neck of efferent fibres of the vagus nerves on either side differed according to the form of the stimulus applied.4. Threshold stimulation of the vagus nerve caused closing of the orifice which was blocked by atropine.5. Opening of the orifice and disappearance of spontaneous closing movements followed more intense stimulation of the vagus nerves.6. Vagal opening effects were obtained after atropine was given and after adrenergic opening and closure effects had been blocked with phentolamine and propranolol.

Animals↗