Some folk around here already use "I don't give an R.A" which in actual fact doesn't make grammatical sense... and neither does .. 'AN' Arzay unfortunately.   It is of course 'A' rat's hindparts not 'AN'... so perhaps we better think again..... Also .... it is probably just as quick to say   " I don't give a rats arse" as it is to say "I don't give an Arzay"... sorry Bruce but a rats arse is a rats arse!!!!! however you look at it.... that's of course assuming you want to look at it!!! LOL
Best wishes, Mike.