1. יוצא דופן and the animal born afterwards: בכור לדבר אחד

The next Mishnah states: יוצא דופן והבא אחריו – regarding [a firstborn animal] born through caesarean section and the naturally-born [animal] which came after it, Rebbe Tarfon says each of them might be a bechor. Therefore, שניהם ירעו עד שיסתאבו – both of them graze until they develop a blemish, after which they may be eaten by their owners. Rebbe Akiva says that neither is a bechor: הראשון מפני שאינו פטר רחם – the first, because it is not the first to open the womb, והשני מפני שקדמו אחר – and the second, because another preceded it. The Gemara explains that Rebbe Tarfon is uncertain whether בכור לדבר אחד – a bechor in one respect is halachically considered a bechor or not. Thus, each animal in our case is a possible bechor: the first animal is the firstborn, while the second is the first to open the womb. Rebbe Akiva is certain that בכור לדבר אחד is not a bechor.

1. Until when a purchased animal’s offspring is assumed to be a bechor

The third Perek begins: הלוקח בהמה מן העובד כוכבים – if one purchases an animal from an idolator, and does not know whether it has previously given birth, Rebbe Yishmael says that if a goat gives birth within its first year, the offspring definitely belongs to the Kohen (because it could not have given birth twice in its first year). The same applies to a female sheep within its second year, and to a cow or donkey within its third year. Any offspring born after any of these respective times is a ספק (thus, for a kosher animal, the owner keeps it and may eat it after it develops a מום; for a חמור, he separates a lamb to redeem it, and keeps both). Rebbe Akiva says that Rebbe Yishmael would be correct if only the birth of viable offspring exempts the mother from bechor. However, even a miscarriage exempts the mother, and the Sages said: סימן הוולד בבהמה דקה טינוף – the sign of a miscarried offspring in small livestock is “soiling” (i.e., discharge indicating a dissolved fetus); for גסה – large livestock, it is a שיליא – an afterbirth (a sac and placenta), and with a woman, it is שפיר – an embryo or a שיליא.

1. Rebbe Meir is חייש למיעוטא, but the Rabbonon follow רוב even for רובא דליתיה קמן

The Gemara asks why Rebbe Yishmael rules that a goat’s offspring after its first year is a ספק בכור: we should follow the majority, and most animals conceive and give birth during their earliest time period, so the next offspring should definitely not be a bechor!? Does Rebbe Yishmael hold like Rebbe Meir, דחייש למיעוטא – who is concerned for the minority, since a minority of animals do not give birth their first year? The Gemara suggests that even the Rabbonon, who follow the majority, only do so ברובא דאיתיה קמן – with a majority which is “before us,” such as תשע חנויות – nine kosher stores and one non-kosher store (where meat found in the city is presumed kosher), or regarding Sanhedrin (where we follow the majority opinion). In contrast, regarding רובא דליתיה קמן – a majority which is “not before us,” i.e., a statistical majority, perhaps the Rabbonon are also concerned for the minority. However, the Gemara proves otherwise: Rebbe Meir does not allow a קטן or קטנה to perform יבום, out of a concern that the boy will be found a סריס, or the girl, an אילונית. The Rabbonon say that we follow the majority of קטנים, who mature normally. Therefore, Rava concedes that Rebbe Yishmael must hold like Rebbe Meir. Ravina answers differently on the next Daf.