It is natural for a woman to breastfeed a child. It is not natural for a human to drink another animal's breast milk. It is also a matter of consent.
There is a lot of death and cruelty involved in the dairy industry: cows are artificially inseminated over and over again to bare calves who, if female are subjected to the same terrible fate, or if male, are slaughtered. There is no death involved or cruelty in breastfeeding a baby.