There is an allowance in the Islamic religion for cow killing, but not en masse as currently being practiced. It's reasoning is very scientific from the karmic point of view, although such allowances are now being taken advantage of.
Prabhupada: Yes. In Arabia they were to eat animal but to save him from so many dangerous and sinful life -- he has to kill so many goats -- better kill one life, a camel or a cow. Camel is big animal. So if you kill one animal, camel, it is equal to fifty goats.
Tamala Krsna: What about a cow?
Prabhupada: A cow is also big animal.
Tamala Krsna: So they say like that?
Prabhupada: Yes... They don't say cow. They say better kill one big animal. "So instead of becoming sinful for killing so many animals, you better kill..." And that is also sacrificed in the mosque, and that is called koravani. Restriction is there.
Tamala Krsna: So there's no... The karma for killing many goats is more severe than killing one cow.
Prabhupada: No, no. You become responsible for each and every animal.
Tamala Krsna: Irrespective of what kind of animal.
Prabhupada: Yes. Now if you can serve the purpose by killing one animal, why should you take the risk of killing many animals?
Tamala Krsna: Even if that one animal is a cow.
Prabhupada: Yes. Animal is animal. And we say protect cow from economic point of view, krsi-go-raksya-vanijyam [Bg. 18.44]. Without saving cows you cannot get good food, not from the animal point of view. You require milk and milk preparation.
January 22-23, 1976, Mayapura