Liver Damage can be there also from Fasciolosis and even bad Acidosis all can add to cumulative effects.Its utter rubbish. The toxins in ragwort are flushed out in the urine, its the process of removing them from the body that damages the liver. There is no 'build up of toxins' in the liver of an animal thats eaten ragwort, just a cumulative deterioration of the liver until it reaches a point when it doesn't function any more. Rather like liver disease in alcoholics - they don't have a 'build up of alcohol' in their livers, they just have damage caused by years of their liver having to process lots of alcohol.
That being said I could well imagine that a ragwort damaged liver wouldn't be good to eat, but that wouldn't be because it was full of 'toxins'.