We have learned that activities that are essential for food preparation are permitted on Yom Tov, based on Sh’mot 12:16. Among the activities that are part-and-parcel of preparing a holiday meal is Sheḥiṭa – ritual slaughter – without which fresh meat would not be available. [It should be noted that modern innovations such as refrigeration have relegated Sheḥiṭa to commercial slaughterhouses, and the kosher kitchen rarely deals directly with such halakhot.]
Some animals – specifically fowl and undomesticated animals – require a ritual called kissuy ha-dam, covering the blood of the slaughtered animal (see Vayikra 17:13). The Mishna (2a) takes for granted that a person can, theoretically, slaughter an animal for its meat on Yom Tov, but what should be done about covering the blood? Plowing and other types of digging are forbidden on Shabbat and Yom Tov; the act of covering the blood – while an important mitzva in connection with the act of Sheḥiṭa– cannot be considered an essential part of food preparation.
The Re’ah explains that even Beit Shammai agrees that there has to be some level of preparation prior to the holiday for covering the blood. Thus he does not permit digging, rather making use of an implement that already was in the ground.