Giving soya milk due to cows milk diarrhea?

[Berangere]

DS 13 months has been waking up at half 5 every morning with a huge, really smelly wet poo. No changes to his diet or routine at all.

Only thing I can think of is that we’ve started to add cows milk to his evening bottle (often around 210ml) to use up the last of his formula and get him used to it. He already has about 120ml of cows milk in the morning, and often some at nursery but not every day. He has a fairly big poo around 30 mins after his first bottle.

My main thought is maybe his body isn’t digesting the cows milk overnight as it’s quite a lot in comparison to the morning bottle, and even in the mornings it can be quite loose.
He doesn’t seem affected by dairy items like yogurt or cheese.

Has anyone else transferred baby onto growing up soya milk? Any pros or cons? I don’t know what else to do at this point.

My son was frequently sick after the transition to cows milk so we changed to no sugar oat milk and it literally stopped overnight!
He still has cows milk on his cereal/at nursery and dairy products so I think his was the same - not an allergy but finding it difficult to digest. I checked with the HV and she said it was fine so I’d definitely look at milk alternatives like you have to see if it eliminates the problem ☺️

Alpro growing up Oat milk is great and fortified for children

My first had cmpa so when they cut his prescription formula at 2, we switched to barista oat (mainly because soya proteins are v similar to dairy proteins). Oat is great for the whole family though, I've switched my tea to oat (when pregnant with second, but she's allergy free) and it's lovely.