Crystals in Dogs Urine

[DobieGirl]

Does anyone know much about Canine Bladder infections? My 2 1/2 year old Male doberman got one in January, the vet put him on antibiotics and took a urine sample (which showed no crystals) however a week after he was finished the meds, it came back! I called the vet and they said sometimes the dog just needs to be on the meds a bit longer, so he gave me more. All seemed well but Today he stared peeing blood and dripping it everywhere. I took him to a new vet and she took a urine sample and apparently he was FULL of crystals. She gave him some strong antibiotics and wants a new urine sample in 10 days. I was a little overwhelmed at the time and forgot to ask her what exactly crystals in the urine mean. I know what they are, but what causes them? Can a dog be prone to getting them? Is there anything I can do to prevent them if that is the case? He doesn't seem to be in any pain and she did a prostate exam which was normal. Also, this could be way off topic but there is a female in heat here and he is not allowed near her (he is not neutered) so he has been very sexually excited around her crate for the last few days, could this have caused the infection? I would appreciate any help anyone could give him. Thanks!

[DobieGirl]

Oh, I should also mention. That they are struvite crystals.I recently switched his food as well. He grew up on Pro-Nature which I love, but I moved in november and where I am now, I can't find it so I switched him to Techni Cal. He then got his first UTI but there were no crystals. My brother and his wife decided to switch their dogs to Performance Nutrition, it looked like a good food so I did as well, since then he got his most recent UTI and is FULL of crystals. Could the new food have anything to do with it?