The Golden problem is enthusiasm, not reluctance
Move a Golden Retriever onto a new diet over about a week of gradually shifting mixes — not because this dog will refuse it, but because a Golden will happily eat a full bowl of brand-new food on day one and present you with the digestive consequences by evening. The transition plan for this breed is really a pacing plan for the owner. Measure the total portion exactly as you did with the old food, change only the proportions inside that portion, and let stool quality, not appetite, decide when to advance. A Golden's appetite will vote yes at every stage, including the stages its stomach is not ready for.
Why measured stages matter for this breed in particular
Golden Retrievers are large dogs with a well-earned reputation for loving food and gaining weight readily once past puppyhood, and a diet change is a classic moment for quiet overfeeding: the new food looks different in the scoop, the dog seems extra delighted, and portions creep. Extra weight is unkind to any large dog's joints, and this breed's hips and elbows deserve the protection of a stable waistline during the switch. There is also a fairness point — if the new diet is being introduced for the dog's health, letting the quantity drift undermines the change you are making.
A week's blending, Golden style
For the first two or three days serve about a quarter new food mixed through the familiar food, then half and half for two or three days, then mostly new, then the new food alone. Because a Golden will excavate nothing and inhale everything, thorough mixing matters less for pickiness here than for honesty: a blended bowl means the dog truly ate the stated ratio. Keep weighing or using the same scoop, count training treats within the day's food rather than on top of it, and brief everyone in the house — Goldens are famously successful at convincing a second person that no one has fed them yet.
Keeping a food-loving dog settled during the switch
Feed at the usual times in the usual place, and resist using the new food as an exciting event; a calm routine keeps a Golden from bolting meals even faster than usual. A slow-feeding bowl or scattering part of the meal in grass for a sniff-and-search game can stretch a fast eater's meal out, though during a transition a plain bowl makes it easier to see that everything was eaten and nothing was left or sicked back up. If stools soften at a stage, hold there — the dog will not mind eating the same mix for extra days, which is the great advantage of transitioning a breed that greets every bowl as the best one yet.
Watching weight and digestion together
During a Golden Retriever's transition, run your hands over the ribs weekly: you should feel them under a light covering, and a change during the switch weeks means portions, not the recipe, need adjusting. Loose stools that persist past a couple of days on a steady mix, repeated vomiting, blood in the stool, or a Golden who uncharacteristically refuses food and seems dull all warrant a veterinary call, since refusal in this breed is a louder alarm than in a fussy dog. Log each day's mix and a quick condition note in KinsLe, where Care Teams timestamps every completed feeding so the whole household can prove who fed the dog and what was in the bowl.