LOIN INJECTION SITES IN PIGS AT SLAUGHTER - A CLASSIFICATION BASED ONHISTOPATHOLOGIC CRITERIA

Injection sites represent an important economic threat to the pork mea t industry. A comprehensive classification of injection sire lesions b ased on histopathology is proposed and discussed. Lesions consisting o f muscle streaked with haemorrhages and surrounded by oedematous and h aemorrhagic connective tissue were attributed to antistress drug admin istration. Acute lesions, with pale brown muscle, bright or dry in sec tion, often stained by haemorrhage and occasionally by chemicals, were similar to those observed after recent administration of antimicrobia ls drugs. Histology revealed myodegeneration andro necrosis of muscle fibres. Macrophagia, neutrophilic infiltration, oedema and haemorrhage were common. Older lesions consisted of fibrosis, sometimes associate d with encapsulated necrotic muscles. Woody callus was characterised b y the replacement of injection-site blemishes with organised white to dirty brown connective tissue and fat, apparent in the histological ex amination as immunologic granulomas. Abscesses were attributed to seps is.