Puppy Protection Act of 2021 This bill requires the Department of Agriculture to expand standards that govern the humane handling, care, treatment, and transportation of animals to include new requirements for commercial dog dealers. Specifically, the standards must require dog dealers to provide to dogs adequate housing, exercise, and veterinary care; appropriate and nutritious food; continuous access to potable water; and meaningful socialization with humans and compatible dogs for at least 30 minutes each day. The standards must also include requirements for breeders to use safe breeding practices and make all reasonable efforts to find humane placement for retired breeding dogs.