Cheap chicken breasts can shrink by almost half when cooked on account of the water pumped into them - and yes, it's injected under pressure, along with phosphates as a binder, to make sure the water doesn't leak out. The process is called "plumping"
When the cats refuse to eat the stuff, you know it's not worth bothering with. Their noses and taste buds are far more sophisticated than mine, and I trust their judgement on all things meaty and fishy LOL.
A false economy to buy the cheap chicken breasts IMHO - even on sticker. I'd be willing to wager that on *cooked* weight, they'd be about the same price per kilo as the more expensive high welfare (and less shrink-prone) ones. That said, all meat loses volume when cooked, but there's a difference between natural shrinkage and artificial shrinkage due to excess added water (chicken & wet-cured bacon) and added fat & rusk (cheap sausages).
If you *must* have breast meat, then it's worth spending more for the higher welfare stuff, but that can get seriously spendy. You're better off buying thighs if you want to keep things sensible, as a) they've got far more flavour, and b) they aren't loaded with extra water. Or buying a whole bird and portioning it up.
