Use of electronic leg tags for identification of small ruminants.

Few studies have evaluated the use of electronic leg tags for identification of small ruminants; thus the objectives of this study were i) to quantify the degree of development in the body region where the tags are placed, ii) to assess the effect of the farm management system on the suitability of the leg tags, and iii) to assess tag readability under dynamic conditions, i.e. as animals moved through a raceway. In three experiments, leg tags were applied as follows: 24ewe lambs and 24 kid goats (Experiment 1); 37 kid goats (Experiment 2); 1,519 goats and 248 sheep (Experiment 3). At 2.5 months of age, the metatarsal perimeter of ewe lambs and kid goats was 80% of the adult values; at 6 months of age, the metatarsal perimeter had reached 90% of the adult values but live weight had not exceeded 65% (Experiments 1 and 2). In Experiment 3, the retention rates of tags on farms where animals were housed indoors were between 99.2% and 100% after one year. On the farm where animals grazed natural pasture the retention and readability rates six months after tagging were 63% and 78.2%. Dynamic readings indicated 100% efficiency. In conclusion, the selection of the leg of replacement animals for attachment of these tags is appropriate because their normal development is not impeded. For different breeds, it might be necessary to identify the optimal age for tagging. Extensive rangeland grazing systems can reduce the retention of leg tags. The electronic tag evaluated in this study showed a high readability rate under dynamic conditions.