Immunity Boosting

Question
I have a 4 and a half month of Boxer female who has had numerous health problems. It began with very frequent urination when she was only 8 weeks old. We quickly discovered she could not concentrate her urine and most likely had a UTI. We did a round of antibiotics that you would expect to work for a puppy her age. Two weeks later we almost lost her, the infection was massive. She went to a specialist, had an ultrasound, and we discovered that the UTI was so severe it had inflamed her ureter and done some damage to her kidneys. The culture revealed the bacteria was e-coli of the bladder. After 5 weeks of heavy antibiotics (Clavamox 125mg 2x/day) she seemed like a happy puppy. 10 days off of the antibiotics she was listless and clearly infected again. Her culture shows the antibiotic is still sensitive to the infection; we've given her the tools to fight it but her body can't seem to kick it alone. She also still has not concentrated her urine so we believe she may have DI as well. Our vet believes her immune system is compromised so while we may be able to keep the infection at bay, her body might not be able to completely get rid of it. Our vet has put her on Cephalexin 500mg 2x/day long term, after seeing another white blood count over 25,000. We've also started her on a probiotic fat-free organic yogurt to help ease the stress of antibiotics. She eats Evolve (all natural)puppy formula as of right now. We don't like the idea of having to keep her on antibiotics for the rest of her life. I believe that with the right diet/supplements we could boost her weak immune system. The catch is my boyfriend and I are both full-time students with jobs and don't necessarily have the time or resources to cook her organic homemade meals. Are their simpler additions or changes we can make to her diet to help drastically boost her immune system and maybe kick this infection entirely?
Thanks so much,
Katherine

Answer
I would continue to work with your vet or maybe even get a second opinion.  It was a much lesser problem, but after her second UTI, my vet put one of our puppies on Science Diet C/D.  That was the end of her problems.  

While a healthy immune system requires good nutrition, there is nothing beyond it that will help the immune system.  The Science Diet C/D work for my puppy not because of its wonderful ingredients, but because it was formulated to meet the standard nutritional profile while lowering the pH of the urine.  The smaller companies that sell Evolve don't have the resources for research and testing larger companies do.  They often pay other companies such as Diamond and Menu foods to make the food.  Nearly all the foods that were recalled, no matter what the brand, were made by those companies.  None of the products made by the larger companies themselves had any problems.  Much of what you read about dog diets is cleaverly worded to deceive you without outright lying.  

The internet of full of cases of people going from one premium food to another trying to solve their dogs problems.  In the real world, most dogs are doing fine on the common brands.  It is possible the Evolve lacks something she needs for good health, but is rich enough to promote joint damaging rapid growth.  You should be feeding an all life stages food now. Switching to an adult chow for the larger breeds at 4 months, slows growth and helps develop sturdier joints.  You do want to make sure what ever you feed has less than 1.5% calcium by analysis, not the minimum on the bag.  Unless your vet thinks the Science Diet C/D would help, I would switch to Pro Plan or Iams adult.  My 6 month old Lab has been on Pro Plan for about 2 months now.  The dog guide school she belongs to breeds hundreds of puppies a year, and X-Rays every single one.  Nobody has more experience or incentive to produce healthy large breed dogs than the service dog schools.  

Much of what you read about dog diets is marketing hype.  There are those that devoutly believe if it is more expensive, it must be better.  Yes, I love a steak dinner, but often end up eating a chicken casserole.  Good nutrition doesn't require expensive ingredients.  Home made has a very poor record.  Yes, many people do seem to do a good job of it, but many fail.  Also, some of the problems show no symptoms until the dog has fatal organ damage.  Don't put time and money, you don't have, into what could do harm to your dog with little likelihood of helping.  Rescuing your dog from its health problems by cooking its meals has lots of warm fuzzies, but no facts to back it.   

Over weight leads to all sorts of health problems, but often Boxers keep themselves lean.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them. Each dog is different. Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx