Cannibalism Is An Acquired Taste.

Thousands of slaves were killed every day to feed them. If there were any hatchlings that couldn't bear the miserable cries of agony or the sight of blood as the livestocks were slaughtered, then they must have gotten used to it by now. 

Some hatchlings became bored of death. The death of livestock couldn't excite them anymore and the life of livestock became worthless to them. Other living things that aren't Supreme beasts might as well be insignificant ants to them. 

Some hatchlings, on the other hand, became conditioned by the cries for mercy. The cries invoke their appetite for flesh. They may be tired one moment but they begin anticipating food as soon as a livestock is forced onto the chopping slab. 

Despite this development, their guides didn't let them stop from eating more livestock. Legion-5 knew what their managers were up to. He is even grateful for it so he made sure to eat as much as he could every chance he got.