Having had animals in the family all my life I know 2 things to be true.
1) never trust any animal no matter how much you think it is a perfect angel. Esp predator animals (dog, cats) around children and livestock.
I cannot count the amt of times I have heard people say ‘I can’t believe Old Roy bit that child, he has never done that before’.
Even prey animals are capable of killing, a horse or cattle can be a serious danger, so can a chicken - just ask my eye dr, who although laughed with glee when I told him how my eye got pecked, did inform me the scratches on my cornea were very bad.
2) an animal has its own agenda (same as you or I), yep you may think you have them ‘trained’ but it only takes one time for that training to fall apart. Dog, cat, horse, chicken, cow, etc. they are living creatures and they have good and bad days just like we do, if they are having a crappy day you can bet your sweet petunias they will take it out on something. And even if the chicken is not the intended victim they can and do get caught in the cross fire of other animals disagreements.
Trust me - been there and have the scars from being ‘accidentally’ caught between 2 scrapping horses, goats, chickens, cats, dogs, and yep people!
Remember - living creatures need to be respected, which means keeping an eye on.