On yesterday’s daf we were introduced to the mitzva of kissuy ha-dam – the obligation to cover the blood of fowl or undomesticated animals that are slaughtered (see Vayikra 17:13). Thus, someone who performs Sheḥiṭa on chicken or venison would be obligated to cover the blood, whereas Sheḥiṭa on cattle – e.g. cows, sheep, goats – would not be obligated in this mitzva.
The Gemara on our daf introduces a koy – an animal that has the features of both a wild animal and a domesticated one – and rules that such an animal cannot be slaughtered on Yom Tov, since it is not clear whether slaughtering a koy obligates the shohet in kissuy ha-dam. Were it not Yom Tov, we could simply cover the blood without reciting the blessing. Since it is Yom Tov, however, we cannot permit a melakha to be done if there is doubt as to whether it is truly an obligation in this case.
Identifying the koy is a difficult task. Even though it is mentioned many times in the Mishna and Talmudic literature, that is not because it is a common animal, rather because its status between a wild and domesticated animal allows it to be a test case for many halakhot. The disagreement as to its identification began in the time of the Mishna, when some of the Sages argued that it is the offspring of a deer or similar animal with a goat. Others claim that it is a unique type of animal – an Ayal ha-bar.
The Ayal ha-bar can be identified with the ovis musimon, which, according to many, is the forerunner of domesticated cattle. It is distinguished by its short hair and grey color, and it lives in mountainous regions, where it is a nimble climber – today mainly in uninhabited areas in Europe. It is likely that the clear similarities between a koy and a sheep, together with its being a wild animal, led to the Sages’ confusion about its classification.
Its name – koy – and even the pronunciation of the name, are themselves the subject of disagreement.