The whole point of these products are to move away from stuff like that. Adding beef blood is like taking a step backwards.
It could be done in a way that isn't cruel. Just take a little at a time, like we do with humans. It might not even be less efficient if the rate of blood production is fairly constant. (I don't know enough biology to speculate.)
It's cruel to take a human's blood without their consent, even if done painlessly.
I don't think it would be cruel for animals, because once you remove pain as a factor, the only suffering left for humans exists on a psychological level that I don't believe animals would experience.
Okay, I don't believe you would suffer at a psychological level either, does that give me the right to take your blood without your consent?
What for though?
Cant you spice something in a particular way instead of bleeding an animal?
Maybe it's not necessary. My point is just that it would be possible.