Nothing but disposable syringes and needles here - and every animal gets its own new sterile needle. OK, steers do get injections with needles that have been in another animal, but they're not gonna be around past 8-10 months.
They're cheap.
Crazy, you say?
Do you know the status of your herd for Bovine Leukosis Virus or Anaplasmosis infection? If you have animals infected with either of these pathogens, every time you stick in a needle that was just used on another animal, you're risking transfer of those diseases - and any other blood-borne pathogen.
I used to use the same needle 'til it got so dull you couldn't drive it through the skin any longer - and was in-and-out of bottles of vaccine/drugs with those same needles; as a result, when we got tired of losing cows to lymphosarcoma a few years back and tested the whole herd - 90% of adult cows were BLV-positive. I'm largely responsible for spreading it throughout my herd - and I knew better.
Yes, it's a PITA to change needles between animals, but I should have been doing it all along.