Brain damage in sheep from penetrating captive bolt stunning.

OBJECTIVE: To determine the severity and distribution of structural changes in the brains of adult sheep stunned by penetrating captive bolt. PROCEDURE: The unconstrained heads of ten, anaesthetised, unhorned, 2-year-old Merino sheep were impacted at the summit of the head with a penetrating captive bolt pistol. Six sheep were ventilated and four received no respiratory support. Two hours after impact, brains from the six ventilated sheep were perfusion-fixed with 4% paraformaldehyde. Sixteen whole, serial coronal sections from each brain were stained with haematoxylin and eosin and immunohistochemically for amyloid precursor protein, a sensitive marker of axonal and neuronal reaction in the brain after trauma. Pathological changes in these brains were then quantified by morphometric analysis. RESULTS: Structural change in all impacted brains was a mixture of focal injury around the wound track and more widely distributed damage in the cerebral hemispheres, cerebellum and brainstem, but varied considerably in severity between individual sheep. All nonventilated sheep died rapidly following respiratory arrest. CONCLUSIONS: After penetrating captive bolt stunning, damage to the central reticular formation, axonal connections, and the cortical mantle is the likely reason for failure of respiratory control and traumatic loss of consciousness.

Regional distribution of glutamate in the central nervous system of rat terminated by carbon dioxide euthanasia.

Carbon dioxide euthanasia is an established method for the termination of small laboratory animals. It has also been employed by the authors in neurobiological research on the post-mortem glutamate concentration in the structures of rat brains. The following investigations were aimed at optimizing the termination procedure based on the CO2 saturation rate of the inhaled air. Two rates of CO2 flow were applied, and the higher one significantly augmented the glutamate level in the hippocampus and cerebellum. The relationship between this finding and signs of central fear reaction is discussed. The authors conclude that lower rather than higher CO2 flow in euthanasia procedures is gentler and is therefore preferable for use with laboratory animals.

Method for determination of pentobarbital in dry dog food by gas chromatography/mass spectrometry.

A procedure has been developed and validated for measuring the concentration of pentobarbital residues in dry, extruded animal feed in the range of 3-200 ng/g (ppb) with an estimated limit of quantitation of 2 ppb. The method was developed for surveillance purposes: to measure the concentration of euthanizing agent which might be present in feeds incorporating rendered products which themselves might include some fraction of euthanized animals. A previously published qualitative procedure was modified by adding isotopically labelled pentobarbital as an internal standard. Dry feed was ground and extracted with methanol. The extract was loaded on a mixed-mode (C-18, anion exchange) solid-phase extraction cartridge designed for barbiturate residues. Pentobarbital was eluted and derivatized for gas chromatography/mass spectrometry in positive ion chemical ionization mode. Quantitation was based on the ratio of dimethyl-pentobarbital MH+ (m/z 255) vs dimethyl-pentobarbital-d(5) (m/z 260) in standards and extracts. Accuracy ranged from 112% at 3 ppb to 96% at 200 ppb, with relative standard deviations ranging from 4% at 3 ppb to 2% at 200 ppb.