Individual identification of pigs

Ann-Sofi Bergqvist¹, Christina Eliasson², Lena Eliasson-Selling³ & Anna Wallenbeck²

¹ Division of Reproduction, Department of Clinical Sciences, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden ² Department of Animal Breeding & Genetics, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden;  ³ Swedish Animal Health Service, (SvDHV), Uppsala, Sweden

Individual identification in pigs is a key feature for management, traceability, breeding, trade-, and disease control. Conventional identification methods used for pigs such as ear-notching, ear tags and tattoos, are not sufficiently efficient due to losses and code erasing.
The purpose of this pilot project was to examine the possibility to use injectable microchips for identification in pigs. The aim was to study retention rate, functionality and tissue damage of microchip routinely used for identification in cats, dogs or horses, when injected s.c. in the ear of fattening pigs, compared to conventional ear tags.

A total of 69 pigs were marked with a plastic ear tag in the left ear at 4 weeks of age, and with an electronic microchip s.c. in the right ear at 10 weeks of age. The readability of the two identification methods was recorded every second week during the growing finishing period and at slaughter. Moreover, ears were collected at the slaughter plant and tissue damage in connection to the ear tag and chip was assessed as damage and no damage. Two pigs were culled during the growing finishing period due to lameness and 1 pig was not identified at the slaughter plant. Descriptive statistics were estimated, and chi-square tests were performed with procedure FREQ in the SAS package.

No apparent animal health problems were during the experiment. During the growing finishing period, 13 pigs lost their microchips but no microchips had moved to other body parts.Of the 66 pigs examined at slaughter, 18.2 % could not be identified by the microchip while only 9.1 % had lost or unreadable plastic ear tags (p=0.128).. Of the ears with readable identification (microchip or ear tag), a significantly lower proportion of chip marked ears had tissue damage in connection with the chip (11.4 %) compared to control ears with damage in connection to the ear tag (88.6 %) (p<0.001).

This method meets the requirements of an identification system for pigs that is unique, easy to read, does not produce apparent disturbances to the animals and minimal pathological changes. However, a non-acceptable number of microchips were lost after application. The reason may be too large size of the chip and the needle used for injecting them which probably made the chip fall out before proper healing of the skin.