In principle, but they probably contracted this out decades ago. Theres a lot of licensing requirements and regulations surrounding dairy.

This is actually the real source and meaning of the classic track by Captain Beefheart & the Magic Band, "Safe as milk." Dairy is a huge systemic risk, operates on extremely narrow windows everywhere in its production and if left unmanaged will cause outbreaks of horrifying diseases like Typhoid.

It's not a problem to be solved from McD corporate's perspective.

... If incentives were properly aligned to make this the correct strategy, then this is probably what McDonald's would do. Unfortunately not. https://www.today.com/food/trends/why-is-mcdonalds-ice-cream...