HI,
We tag (dangle tag) and RFID tag all of our calves/cows/bulls. We try to get as much info out of the number without getting so complicated it becomes cumbersome. The first calf gets a 1 and a letter to denote the year. This season the first calf will be 1-W, then 2-W, etc. Every calf gets a unique number. This is important for tracking in our database. We don't ever change the tag number so as to avoid confusion and maintain integrity and confidence of our data. We use the calfs, cows, bulls, unique ID in the database to track lineage, stats, innoculations, etc. We put the dangle tag in the right side (passenger side) ear of the bull calves and left side of a heifer calf. We do this to making later sorting a little easier and because the heifer will receive a tattoo in her right ear later on when she gets her bangs vaccination. By looking at a tag we know where the calf was born in sequence to the herd and the year the animal was born. We can also tell the sex if the head shape isn't obvious and/or the angle just isn't right for a quick decision (gate cutting).We know some who use the year as the first number, like 9001, where 9 denotes 2009 and 001 is the first calf. this is a problem if you retain cows older than 10 and need a unique ID for every animal (i.e. most computer systems). All RFID buttons go deep in the left (driver side) ear. We use RFID for our ASV (age source verification) process and to automate our working process. As a cow or calf steps into the chute the scanner will read the tag and bring up the animal in the database. Then we can scan the monitor for any notes ( i.e. open, picked for culling, needs feet checked, or any other note we need to remember at working time). We can then press one button to apply a current weight and innoculations to that animals' data.