The administration of intraruminal identification boluses to a group of 76 lambs resulted in 24 (32 per cent) showing signs of pharyngeal damage. In 16 of them the bolus was found to be in the retropharyngeal region by means of a hand-held microchip scanner, radiography and endoscopy. Purulent tracts were identified in the dorsal pharynx. In 13 of the 16 lambs the surgical removal of the bolus under general anaesthesia was followed by a normal clinical recovery, although the lambs did not grow as well as similar unaffected animals; three of the 24 lambs died. The administration of a larger bolus to 10 yearling rams did not result in any clinical signs of pharyngeal damage. The most important factors influencing the occurrence of this type of injury among this group of lambs were the size and age of the lambs, the positioning of the lambs during bolus administration, the relative size of the dosing gun and bolus, and the large number of animals in the group.
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