HISTOLOGICAL-FINDINGS AROUND SUBCUTANEOUS LY IMPLANTED TRANSPONDERS IN CATTLE

Electronic identification of animals using injectable transponders is of increasing importance for the identification of ownership and traci ng, as is the recovery of such implants in slaugther-houses. A trial w as conducted to reduce potential migration of the implants and to prov ide a visual aid for their recovery at slaughter. Three groups of anim als were used: Group 1 received a transponder in bioglass, which is in ert, collected ten months (n = 11) and twelve months (n = 26) after ap plication; Group 2 received a similar transponder, but covered with a net of polytetrafluorethylene (PTFE) (n = 11) collected after ten mont hs, and Group 3 received a transponder covered with PTFE and dipped in green tattoo-colour ink (n = 25) which was collected after 12 months. No local irritation was observed. Macroscopically, all transponders w ere encapsulated by a thin connective tissue layer, and the green ink was always detected easily. Histologically, in Group I in all but five cases the inner zone of the capsule was inflamed with necrotic areas. In five of these cases also granulomas in the periphery were prominen t. No differences between the materials 10 and 12 months after their a dministration was observed. In Group 2, chronic necrotizing inflammati on with foreign body reaction and focal calcification in the capsule a nd granulomas in the surrounding tissue were seen. In Group 3, the sam e changes were present, but were combined with conspicuous phagocytosi s of colour ink in granulomas. Two cases, in Groups 2 and 3 exhibited chronic proliferative, actinomycosis-type inflammation. The most minim al reactions occurred with the commercially available type of transpon der. The results differ from the results of most studies on tissue rea ctions to transponders. The method of administration may have had an i nfluence on these reactions and this should be improved.