Hi Ptrblk, cows usually have identity tags connected to thier ears that has a 4 digit number of consistent shape and size.
Hi KFrank, thank you for your detailed “how to”. I will now go and research some more and no doubt may have a few questions.  One of the things I find is that as its a big field of study, I’m trying to bolt together existing solutions to make it all work, although I think I will trash and need to rebuild my ubuntu laptop a few times.  
Would you recommend re-imaging a laptop or maybe working within a virtual machine?
Cheers
Steve