You should find a brand of pet food that works for you, and stick with it.
Changing foods all the time isn't a great idea. It could cause upset in your dogs stomach, as well as cause your dog to become picky.
Royal Canin is a funny brand. When I first read the ingredients, I wasn't super impressed. It looked like a good food, but I would put it at higher end of mid grade ratings.
However it FEEDS REALLY well. Most dogs that eat Royal Canin look really good, feel really good, and eat really well.
RC definatly varies from bag to bag. The Chihuahua formula isn't nessicarily the BEST of all the RC. The ingredients are as follows:
Chicken meal, rice, ground corn, brown rice, soy protein isolate, chicken fat (naturally preserved with mixed tocopherols, rosemary extract and citric acid), natural chicken flabvor, dried egg powder, dried beet pulp, powdered cellulose, salmon oil, potassium chloride, sodium alumino silicate, chicory extract, soya oil, sodium tripolyphosphate, choline chloride, DL methonine, calcium carbonate, taurine, vitimans (I won't type out all of them out, but it contains E, C, B6 and B12, B1, D3, B2, calcium etc) Trace minerals as well. Green tea extract and chondroitin sulfate.
It ahs a crude Protein of 28%, Crude fat of 16%, Fiber of 4.2%, Moisture of 10%, 200mg/kg of glucosimine, and 390 mg/kg chondroitin.
It's calorie content is 336 kilocalories/cup.
The RDP is 3/4 of a cup for a 5lb dog (average sized chihuahua).
The size, shape, smell and ingredients in the food are there to be tempting as well as beneficial to the specific dog - the kibbles are slightly larger than some smaller kibbles to help the dog chew them properly (therefore cleaning their teeth). The food does have a higher grain content which helps for a slightly larger stool (not enough to increase the AMOUNT of times that they are pooping, but enough to make the poop slightly larger) which helps to clean out as it comes out (which can help with small dogs, as a lot of them are prone to needing their anal glands excreted). It brags on the front of the bag to be great for fussy small dogs with "exclusive savor", it claims to have tarter reduction effects, and help with stool odor relief.
I have a chihuahua who eats the royal canin. However, he does not eat the Royal Canin Chihuahua food. I think that 3/4 of a cup is a lot of food for him to eat every day, and I don't really need the corn to be that high in the ingredients. I like grains to be present in the food (as I'm not 100% sold on completely grain free diets, and I do a lot of grain-free treats such as freeze dried liver etc, so he wouldn't get grains from the cookies), but I don't need them to be in that quantity.
I feed him the RC mini special food. The ingredients of this food are: Chicken meal, chicken, brewers rice, brown rice, chicken fat (preserved with mixed tocopherols), corn gluten meal, dried egg, beet pulp, natural chicken flavor, brewers yeast, canola oil, chicory extract, salmon oil, potassium chloride, monosodium phosphate, drietd sweet potatoes, choline chloride, salmon meal, dicalcium phosphate, flax seed, zinc proteinate, citiman E supplemtn, dried blueberries, dehydrated alfalfa meal, dried spinach, marigold extract, folic acid supplement, zinc oxide, iron sulfate, manganese proteinate, biotin, sage, copper proteniate, calcium panthothenate, copper sulfate, manganous oxide, vit A supplement, pryridozine hydrochloride, sodium selenite, rosemary extract, ascorbic acid, niacin supplement, riboflavin supplement, thiamine, ascorbic acid, niacin supplement, riboflavin supplement, thiamine, monotrate, vitiman B 12 supplement, calcium iodate, , vitamin D3 supplement.
Crude protein is 30%, Crude fat is 22%, Fiber is 3%, Moisture is 10%, omega 6 fatty acids min 4.5%, omega 3's are .76%
It has 517 kilocalories per cup.
It recomends to feed 1/3 or 1/2 of a cup a day (varying with the amount of exercise that the dog is doing)
I like the ingredients more for sure, and I like the fact that they put in a few extra fruits and veggies that the chihuahua food is lacking. I also like the fact that because of the higher calorie content the dog is able to eat less. This not only means slightly smaller stool volume (while still having a large enough stool to clean as it is passed), but also your dog won't eat past being comfortable - I find my dog much prefers to eat smaller meals than larger ones.
It also has more fish oil, omega fatty acids, and flax seed for a healthy coat and healthy skin.
I have nothing against the RC chihuahua food - but I'm not completely sold on it. I like that they have adressed that different sized dogs and different breeds have their own unique and individual needs. But I don't think that it should be nessicary to feed a yorshire terrier the yorkie food, or a toy poodle the poodle food. The RC also makes the mini adult 27 food - which is their all breed adult formula. I don't have an ingredients list with me, but it's more similar to the chihuahua, but doesn't have corn so high up in the ingredients.
If I were you I would first of all - find a food and stick to it. Secondly - take a look at what you are feeding your pet and learn to distinguish between a good food and a not so good food.
You say you have used eagle pack - that too is a really good brand of food - the ingredients sounds more impressive than the royal canin, but I don't find it always feeds as well. A lot more dogs tend to have constipation poops, or just a general dislike for the food.
My dog loves his food (and he is a picky eater) he eats it super well every night, and he looks and feels great. He has an amazing skin and coat, his teeth look great ( I do use an enzymatic supplement, but the food can help or hinder!), and he has lots of energy.
If you have any more questions regarding Royal Canin or any other brands of dog foods - I would be glad to help you where I can. You can either PM me or just post back on this thread. hope this helps
Meghan