Simpsons v royal canin

[Runrogrogrun]

Hi all - looking for some feedback/reassurance/comments please

I have a Cavalier KC bitch, around 6 months now, which was weaned onto Royal Canin/natures diet. She was never keen on the wet food so with advice from vet I switched to just the dry. Happy with this. Roll on several months (4/5) I went to an independent pet shop who introduced the idea of moving her onto Simpsons (sensitive) as not cereal based etc. I went home and did my research and indeed it looked better for her. Purchased a small bag (2kg?) which I introduced over a week or so. She loves it. I purchased a big bag (£40ish) which I have just opened (so I guess the small bag has lasted 3/4 weeks). However while she is doing slightly less poos (maybe 3 a day opposed to 4/5 with Canin) she is now very windy (and it stinks) and her stools are formed but very soft/squishy (often very difficult to pick up off grass - not ideal with young children!). Didn't get this with Royal C - no wind, and good firm poops.

She is a bright, happy little pup and her eyes and coat always shines. She has an excellent nose on her (could give my dads gun dogs a run for their money!) and she does gobble her food (I usually use the kong to slow it down for one of her meals) but then this hasn't changed since I have had her, canin or Simpsons. Should I persevere?
Thanks

What does the Simpsons actually contain?

Some dogs don't manage well on potato starch, it could be the protein used, other additions or additional fats or oils. But I'm not familiar with the ingredient list. How is her weight? 4-5 poos a day would make me wonder if she is being overfed (even accounting for the cereal bulk in Canin).

Personally, and it's a bugger after buying a big bag, I would be inclined to stop the Simpsons. If there are no other variables like overfeeding, illness, scavenging on walks, overexercised in hot weather or an increase of table scraps etc then poorly formed poo and wind most likely mean something in that food is disagreeing with her. If she hasn't shown signs of the food swap being done too quickly (which it doesn't sound like it was) then I wouldn't wait to see if she settled on it.
I would also go back on to RC until her stool is firm again and she has at least a month for her gut to recover before trialling any new food.
If this occured only with the big bag I would also ensure there was no sign of mould - this can happen if warm kibble is packaged too soon during a rush or stored incorrectly.

The 4-5 poo's a day would be a concern to me.

My boxers have Royal Canin vetbreed for Boxers and only ever do 2 solid poos each a day.

Have you checked the Simpsons ingredients against the Royal Canins?

Thanks for your replies.

She is not over-fed - the vet is very happy with her weight (and so am I) - at the moment she is all legs! However she is obsessed with food and, if I didn't know better and was sure she was being fed the correct amount, you could easily think she was starving. She is not getting any table scraps only some burns kibble when training (practising!) but this has been the same for months. This Simpsons variety is potato based and has a higher protein content than the Canin - which was why I was recommended it and what lots of forums suggested.
Obviously doesn't agree with my little girl so will probably go back to Canin. And hopefully the poops will reduce and get firmer!
Thanks