Recognised-by-law versus other identification systems in pigs: piglets discomfort evaluation and performance testing

The aim of the study was to evaluate the performance of recognised by Italian law (tattoos) and other (ear tags and injectable transponders) identification systems and to investigate if they caused different levels of short-term discomfort in piglets. Ninety-six ten-day-old piglets – equally assigned to four experimental groups – were identified with electronic ear tags (EET), transponders injected in the auricle base (TAB), in intraperitoneal position (TIP), or ear tattoo (T). Losses, breakages and readability of the identification devices were recorded to evaluate their efficiency. Forty-eight piglets were observed continuously for 5 min after identification. Behavioural indicators of pain, discomfort or ease were recorded in terms of duration of occurrence or frequency. Non-parametric analyses of variance were used to compare time required for the application of the devices and behavioural reactions of piglets. No healing problems or breakages of the electronic devices were observed during the trial. The readability after nine months was 93.8% for EET and TIP, 86.7% for TAB and 0% for T. The time required for the application differed significantly (P<0.001) among the four identification devices. EET and TIP showed better results than T considering losses, breakages, readability and time required for application. Behaviours most frequently recorded were head shaking and ear scratching, observed more frequently in piglets after the application of EET (P<0.001). The application of these identification devices caused a mild discomfort in piglets; further studies should investigate in detail the intensity and duration of reactions to the identification procedure.