How old is old?

Question
One of my guinea pigs has a UTI.  The vet has prescribed Baytril, but cautioned that it can affect growth.  I've been searching high and low on the internet but have been unable to answer what I thought was a basic question.  

When is a guinea pig "old", or in other words stop growing/developing?  

Answer
Rob -

Sounds like you have a vet who has done his research.  Yes, Baytril can affect the growth of a young cavy.  To answer your question, a guinea pig is considered full grown, or mature, at 6 months or older or over 30 ounces (at least according to show standards.)  Keep in mind that the weight may be a question mark for a little while - especially right around the six month mark.  They may keep growing for quite a bit of weight after that (I have a sow right now that weighs in at 45 ounces and boars can be quite a bit heavier.)  Use your own best judgement if you're "borderline."

Hope this is helpful.  If you have any more questions, please feel free to contact me again.  Good luck!

Lorena