It makes commercial sense to treat all the animals the same, but I'm not sure it's a rule. If they don't bless some of the animals, that doesn't suddenly mean that none of the animals are halal.The abbatoir pays for a priest to pray at the beginning of the day and then has to employ muslims to carry out the slaughter. Commercially it makes sense for them to kill all the animals like this and then they have a bigger market to sell to, labelling each as Halal or not as required.
They do communicate it. Tesco and Sainsbury's say that all of their own brand meat is stunned before slaughter.ha, but you cant make that choice as its not communicated. maybe it should be. the issue of stunning is a bit of a modern development, and to me immaterial in the bigger picture. some non-Halal meat wont be stunned and some Halal meat will be stunned prior to dispatch
That's the reason why many who supply halal meat don't stun the animal first, and it's completely daft. If you stun the animal, and then slaughter it, it's not going to have gone off is it. They've also proved that not only are stunned animals not dead, but they can recover if not slaughtered. They've also proved that slaughter without stunning causes more pain, which is against the principle of halal food.like so much with religious guidance there's opinions on whether it applies or not (the strict rule as i recall is that the animal must not already be dead. there is a sensible anthropological reason for this, dead meat is likely to be off.)