http://www.prisonplanet.com/articles/february2005/080205animalidentification.htm
 
This would certainly be a good idea for tracking animals that have an infectious disease with the larger animals having radio frequency identification tags implanted in their ears, and sheep and goats will have implanted chips.  However,  Christians in hiding during the tribulation period wouldn't be able to buy animals to breed so that they would have food to eat since the animals could be tracked unless there was a black market that sold animals who had their chips and radio frequency identification tags removed.