Rif Beitza 4a {Beitza 2a; 7b - 8b}

4a

{Beitza 2a}
Mishna:
If one slaughtered an undomesticated animal {chaya} or a fowl --
Bet Shammai say: He should dig with a spade and cover {the blood}.
And Bet Hillel say: He should not slaughter unless he has dirt prepared {muchan} from while it was yet day {on erev Yom Tov}.
And they admit that if he did slaughter, he should dig with a spade and cover, for the ashes of the stove are considered prepared.

{Beitza 7b}
Gemara:
Rav Zerika cited Rav Yehuda: This was where the spade was inserted {into the earth} while it was yet day.
But is performing crushing {which is a melacha}!
Rav Chiyya bar Ashi cited Rav: It is referring to loose earth {which requires no crushing}.

{Beitza 8a}
"for the ashes of the stove are considered prepared":
{which should rather be: and the ashes of the stove are considered prepared}
Rav Yehuda cited Rav: This is only where it was burnt while it was erev Yom Tov. But if on Yom Tov, it is forbidden, but if it is still {hot enough that it is} fit to roast an egg on it, it is permitted {even if it was burnt on Yom Tov}.

A brayta also says so: When they said that "the ashes of the stove are considered prepared," they only said this when it was burnt from erev Yom Tov, but if it was burnt during Yom Tov, it is forbidden. And if it {still} fit for roasting an egg, it is permitted. If he brought in dirt for his garden or his wasteland, it is permitted to cover with it.

Rav Yehuda said: A man may bring in a full basket of dirt {before Yom Tov} and use it for all his needs.

Mar Zutra expounded in the name of Mar Zutra Rabba: And this is where he singled out a specific corner for it.

And a koi {which is either a chaya or a beheima} is forbidden to be slaughtered on Yom Tov, for they learnt {tnan}: a koi -- we do not slaughter it on Yom Tov, and if he slaughtered it, we do not cover its blood, even if there is dirt prepared, and even with the ashes of the stove.

What is the reason?
{Beitza 8b}
Rami son of Rav Yeva said: As a decree because of the possibility of {wrongfully} permitting its fats {cheilev}. For one who sees that we cover its blood on Yom Tov will come to say that it is a type of chaya {whose fats are permitted}.