The simple asnwer is, it's the ingredients and the quality of those ingredients that make the difference. Look at the ingredients list on a bag of Ol Roy, and the list on your bag of Solid Gold. They will be like night and day.
One will be filled with so much corn, wheat, flour, soy, poor-quality grain fragments, etc...that it looks more like food suited to birds than dogs. The other will be filled with real meat, and quality, easily digestible grains. The quality of the ingredients is also different...low-quality foods, if they use meat at all, get it from "4D" sources (dead, dying, diseased or disabled animals), and these meats, while still living animals, were often pumped full of medicines and chemicals to attempt to treat whatever was ailing them.
They also mostly use by-products instead of actual meat, which consist of everything BUT meat, as well as non-specific meat (such as "meat meal" and "animal digest") which could be literally ANYTHING from actual meat to roadkill to unsold pet store rodents. Quality foods get their meats from quality sources; they get the same meat that would end up on our own dinner tables. The same goes for grains.
Low-quality foods include grain fragments and other reject by-products of the food industry, which provide dogs with little to no actual nutrition, as these grains can barely be digested. High-quality foods, if they do include grains at all, use whole grains, which provide more nutrition and are easier to digest. Also, some points: -You say "recent," but you don't say how recent.
Changes will not appear suddenly within a few days or sometimes even within a few weeks. It will take a few months to see all of positive effects better food has on a dog. Some changes may be minor, and some may be big and very noticeable.
It just depends on the dog. There are also changes you don't see that have to do with general health and digestion that may not be apparent by just looking at the dog. -I'm not sure how you came to the conclusion that fish meal was a by-product, but it is not.
It is real fish, simply with the moisture removed before processing, as opposed to during processing. -You get what you pay for. They produce Ol Roy on literally pennies per pound because they get the ingredients for almost nothing, so they can charge peanuts for it and still make a profit.
Producing high-quality food costs more, and therefore the food will inevitably be more expensive. The company has to cover their costs, and they obviously want to make a profit as well, like any other company does. -No fillers don't make a dog full on less, no fillers means that less food is required to get the nutrition a dog needs.
One reason your dog may be eating more is because the food tastes so much better. Ol Roy is flavorless corn/wheat/soy. Solid Gold is MEAT and quality grains.
It's no surprise that your dog would be more enthusiastic about Solid Gold. Of course, just because your dog wants more food doesn't mean your dog needs more food. Many dogs will eat until they puke if a food tastes good enough, so the fact that your dog wants more doesn't mean she actually needs to eat more.
It's all in the ingredients. Some dog foods I wouldn't feed to a starving pig, they're just terrible. Differences don't appear in a few days, or even weeks(as Amanda said), but in a few months.
Think about it in the long run... What you're spending now on dog food is WAY less than you'd be spending on vet treatments from poor nutrition. If price is an issue, you could also get some cheaper good quality foods. I heard Chicken Soup for the Dog Lover's Soul is a great food for a good price.
Edit- To Amanda- That kind of food isn't even suitable for bird food it's so bad! Maybe wild birds, but I would kill before Calvin eats that stuff as a diet( he eats pellets, trying to get him on fruits and veggies too).
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.