The research I've done is with Golden Retrievers and the quality of ingredients and where the dog food is manufactured (which does make a difference.) Large breed dogs do have different needs and requirements vs. small breed dogs. Dogs that are used in sportsman activities, agility competitions, etc…also have different nutritional requirements.
Dogs are also like humans, and some have faster metabolisms than others and require higher amounts of food. Dog food bags have “recommended” feeding amounts. They are guidelines, and your individual dog may need more or less food to maintain a healthy weight.
Part of the different varieties within the brands is marketing and the demands of the customers vs. the dog's nutritional needs. The bottom line is Goldens do not need corn, wheat or soy, (these are known allergens), and they need a formula that provides slow growth for bone/joint support. While some research has been done, there isn't a conclusion regarding grain-free being linked to dilated cardiomyopathy. Dog food companies are now supplementing with Taurine, which has been the cause of concern.
Supporting your Golden's growth is important.
Larger dogs grow much faster than smaller dogs, and you want the growth process to be slow. A quality dog food for a Golden requires IF your dog is going to be over 70 lbs as an adult, you want to feed a formula with a balanced protein to fat, coupling that with a 1:1 phosphorus to calcium ratio to ensure the bones do not grow faster then they should be. The foods we recommend do this.
We've used Life's Abundance since 2008 and still use it, along with PawTree. When we first started using it, they only had an All-Stage formula, and we raised very healthy puppies without a Large Breed Puppy Food. The key focus needs to be it is an ALL-Stage food and meets the correct ratio for growth for dogs over 70 lbs. We started using the Large Breed Puppy Formula because our families' vets required it, and not feeding it was in conflict with their vet's advice, and it was confusing to everyone.
Why do we extend our guarantee for dog foods we recommend?
Because we have experience with them, know the ingredients, and know where those ingredients are sourced from. We also research whether or not the company has ever had a dog food recalled. We feel this is important because recall is about quality & ingredient control. Are there other quality foods out there? Yes, however, we do not personally have experience with them, and as our vet says, it would be too time-consuming to research and know each brand out there.
We believe nutrition matters (for us humans too), and our dogs & cats depend on us to do our due diligence in feeding them for proper health and growth. If you grow up on fast food, your health will reflect it. Cheap, low-quality foods for dogs are like fast food, and their health will reflect it.
I know this is a lot of information. If you have any questions, let me know.