Well the LEGAL requirement for it certainly is a modern phenomenom BUT the existence of persons who understood care for animals and that animal cruelty is not necessary has always existed. Just like there has always been the complete arseholes who lack empathy, whether for animals or even their fellow man. And these arseholes who have always existed have never cared about cruelty to animals, humans, whatever. A lack of empathy is a definition for evil btw.

In the farming community there have always been some farmers who cared for their animals and limited harm or pain to them. And other arseholes who think nothing of the worst cruelty, whether by inaction. Or by action.

The modern part is legal constraints and obligations.