Dark circles under the eyes are from changes in the blood vessels. It could sometimes be froma chronic skin condition like atopic eczema. Which the later being more common to people with darker skin color. It could also be hereditary or from a lack of sleep. But, I've never heard it be a symptom of liver problems.
My wife had cirrhosis and never had circles under her eyes. Besides the liver doesn't release toxins back into the blood unless it is in liver failure and at that point I wouldn't worry about circles under the eyes. Allergies to air pollen or exposure to sunlight can cause dark circles under the eyes.
And you also said:
I heard if a cow dies they still sell the meat on the markets
It would be hard to eat a cow while it was alive. LOL :-)