During the slaughter and dressing of bovines, there are several conventional practices that disrupt the integrity of the central nervous system, (CNS) and have the potential to disseminate it on edible meat. This applies not only to carcass meat, but also to head meat, possibly contaminated by brain material (which is specified risk material) at, or following, stunning an animal with a captive bolt gun.
Head removal also is an invasive procedure, as the spinal cord is severed, and there may be leakage of brain tissue through the foramen magnum. There is no information on the prevalence or amount of CNS contamination of head meat from cattle slaughtered in UK abattoirs and therefore no basis for an assessment of public health risk from these sources should a slaughtered animal be infected with BSE.
There are many factors that have potential to introduce substantial variability in the degree of contamination of head meat, including abattoir practices and subsequent moving and storage of heads if harvesting meat is performed off-line or in separate premises.
A comprehensive evaluation of the contamination of bovine heads and head meat by CNS material will be based on current industry practices and on a simulation of procedures that would be used if heads were processed at cutting plants.
Contamination will be quantified using CNS marker protein(s) and will be measured on head meat after different handling and harvesting methods currently used. The effects of bunging the captive bolt shooting hole and the foramen magnum (including after brain stem sampling) on contamination of heads will be determined. The effects of surface dehydration of heads during storage on the detection and amount of CNS material will be measured. Two options to simulate loading, within-plant/road transport, and unloading of heads being transferred to a cutting plant will be explored.
A best practice for the procedures involved in shipping heads will be identified and contamination levels after transfer will be compared with that on heads harvested on-line.