• Machlokes if חוששין לזרע האב (re: mules)

Rebbe Yehudah says: הנולדים מן הסוס – [mules] which are born from a female horse, although the father is a donkey and they are crossbreeds, may be mated with each other. However, a mule born to a female donkey is forbidden to a mule born to a female horse, because they are different species. Shmuel says this is only Rebbe Yehudah’s opinion, who holds אין חוששין לזרע האב – we are not necessarily concerned with the father’s seed. But the Chochomim say כל מיני פרדות אחת הן – all types of mules are one species, and permitted to each other. This is Chananyah’s opinion, who said that אותו ואת בנו also applies to the male parent, because he considers it the father’s offspring as well. Since he holds חוששין לזרע האב, a mule born to a female horse and male donkey and one born to a female donkey and a male horse are both considered hybrids of both, and are permitted to each other. The Gemara eventually concludes that Rebbe Yehudah himself is uncertain if חוששין לזרע האב; accordingly, he agrees to prohibit פרי עם האם – the product of a crossbreed with the species of its mother.

• Machlokes about a כוי regarding אותו ואת בנו and כסוי הדם

In a Baraisa, the Tanna Kamma says that אותו ואת בנו applies to a כוי (a crossbreed of a goat and deer), but Rebbe Eliezer says it does not. On this Daf, Rav Chisda ultimately explains that their machlokes pertains to a female כוי born from a male goat and a female deer, and one shechted that כוי and its own offspring. The Rabbonon hold חוששין לזרע האב, so the כוי is considered part-שה, and שה ואפילו מקצת שה – the term "שה" in the prohibition of אות ואת בנו includes even a part-שה, such as this כוי. Rebbe Eliezer holds אין חוששין לזרע האב, so this כוי is fully considered a deer. A Mishnah prohibits shechting a כוי on Yom Tov, since it is unclear if a כוי is a חיה and requires כסוי הדם – covering the blood of shechitah. If one did shecht it, we may not cover its blood on Yom Tov, which violates certain Rabbinic prohibitions. The Gemara proves that the Mishnah refers to a כוי born from a male deer and female goat, and follows the Rabbonon, who are uncertain if חוששין לזרע האב or not. Therefore, it is a ספק if this כוי is a part-deer (requiring כסוי הדם), or fully a goat (and exempt).

• זרוע לחיים וקבה of a כוי

Having proven that the Rabbonon are uncertain if חוששין לזרע האב, the Gemara infers that Rebbe Eliezer, who argues, must be certain that אין חוששין לזרע האב. This is challenged from a Baraisa, in which the Rabbonon say that both כלאים and a כוי are subject to the obligation to give the זרוע לחיים וקבה – foreleg, jaws, and fourth stomach to a Kohen, which is written about a שור and שה. Rebbe Eliezer says a כוי is exempt from these מתנות. The Gemara explains that the Baraisa is discussing a כוי born to a male deer and a female goat. According to the Rabbonon, who are uncertain if we are חושש לזרע האב, it is unknown if this כוי is fully a goat and completely liable for מתנות, or a half-deer, and only half is liable in מתנות. Since this is a monetary question, the burden of proof is on the Kohen, and the owner is only required to give him half the מתנות, and this is what the Rabbonon mean when they say the כוי is “liable.” However, according to Rebbe Eliezer, who is certain that אין חוששין לזרע האב, it is fully a goat and should be liable in מתנות!? Therefore, the Gemara on the next Daf explains their machlokes differently in all the above cases.