From: Rabbi Akiva Eiger
To: Unknown recipient
Rabbi Akiva Eiger addresses the tension between the Rosh's view that rov and chezkas chulin together should exempt a male born alongside a female from bechor sanctity, yet the Mishnah still forbids shearing and labor. He argues that chezkas chulin applies only to a cholevess, not a mevakeres, and distinguishes peter chamor from bechor behemah tehorah based on the availability of a redemption mechanism, concluding with an unresolved difficulty regarding Tosfos' understanding of i efshar letzamtzem.
Source: Shu"t Rabbi Akiva Eiger §167