It could be the hormones that are given to chickens so that they will grow faster and fatter. We absorb these hormones, too, when we eat the chicken.
That stuff about chickens having less fat and so being healthier than red meat is crap, though. Chicken is just as bad as beef, probably worse. And anyway, that whole theory about fat and cholesterol in regard to health is just a misguided theory.
Fat (including saturated fat) and cholesterol are not your enemies.
It's up to you whether you want to be a vegan or continue eating meat, but there are other viewpoints out there. I'd recommend you do some reading at this website: