Why does Picatrix insist to eat liver?

[Hiro]

I've recently read The Picatrix(Greer and Warnock trans) and have been somewhat puzzled with some sentences.
In the book, there are several times asserted that you should kill a sacrificed animal and eat its liver.
For example, in the book 3 chapter 7, there is the conjuration of 7 planets, and all planets except Saturn, the instruction asserted the reader to eat a sacrificed animal's liver after beheading it.

In the conjuration of Jupiter, the following is said,

"...Prostrate yourself to the ground and pray, and repeat the aforesaid (prayer) often and many times. Afterward, take a white lamb and behead it and burn it completely, and eat its liver. Then it will be as you have asked."

Also, about Mars, "Then behead a leopard, if you can get one, and if not, a mouse ... and eat its liver."
In the Sun. "When you have finished, behead the rooster and eat its liver."
In Venus, "When this is done, behead a pigeon and a turtle-dove, and eat their livers."
In Mercury, "behead a rooster that has a large comb, and burn it, and eat its liver."
In the Moon, "if you sacrifice a ewe instead(of a calf), burn her and eat her liver."

Other chapters and books in the Picatrix also asserted eating liver.
I have no idea why the author insists on such instruction. I don't know any other Grimoires and magic/occult books that say so.
Perhaps, is it a tradition of Arabian magic?
I want to know your opinions.