Hard to tell from pics if intestines or yolk sac/umbilical cord, either way euthanasia is your best option if it hasn’t died already, prognosis is awful and a slow death of peritonitis is agony. You might be able to treat a small hernia/unabsorbed yolk sac but if the guts are already protruding or the bird isn’t full term and the belly is still wide open, he’s going to die.