WELFARE OF CALVES .1. INVESTIGATIONS INTO SOME ASPECTS OF CALF SLAUGHTER

The relationship between carotid occlusion, systemic blood pressure an d brain function following electrical stunning and exsanguination (sti cking) in slaughter calves (<10 weeks) was assessed. Electrocorticogra ms, systemic blood pressure and evoked responses were measured in the chloralose. anaesthetised and the unanaesthetised states. Electrical s tunning produced relatively short periods of measurable epilepsy in sl aughter calves (18 s average). The pattern of decline in blood pressur e after sticking showed variations between animals, However, the resul ts indicated that two groups of animals could be recognised: a carotid occlusion (ballooning group) and no carotid occlusion (non-ballooning ) group. The animals with ballooning (six out of 15 = 40%) developed o cclusions of the caudal severed ends of the carotid arteries. These sw ellings, the so-called 'ballooning' effect, were characterised by larg e clots forming plugs at the severed ends of the arteries. When this p henomenon occurred the haemorrhaging was clearly impeded. This was ref lected in the blood pressure traces which showed recovery episodes coi nciding with the occurrence of the carotid occlusions. Our study indic ates that in the worst possible case the development of a restriction to the outflow of blood can delay the rate of haemorrhaging and the de cline in blood pressure. This can lead in turn to sustained brain func tion as evidenced by the continued presence of evoked responses follow ing stun recovery and a long time to onset of the isoelectrical state in the electrocorticogram.