I have a diabetic Lab who we've been managing for about 5 years (since he was 18 months old). I don't and have never fed a prescription diet. I feed Wellness CORE with the addition of 1.5 cups of green beans at each meal for additional fiber. I feel that this allows us to provide a more quality food with the necessary fiber source without resorting to low quality fillers usually found in prescription foods.
If you check out the K9 diabetes forum you will find many people who choose to use diets that are not prescription - I recommend it!
I also recently found that Walmart has insulin for a fraction of what I had been paying at CVS. Given that most Labs go through a lot of insulin, this is a significant savings. I was spending $100 + for a month's supply and now that is down to around $30-35.
Are your Labs siblings? Does your breeder know about their disease?
Sharon, Blaise and Diesel.