How Does the Leniency of "Cholov Stam" Work?

Chazal prohibited all milk unless witnessed by a Yisroel, who must ensure that the milk is only from kosher species (Avodah Zarah 35b, Yoreh Deah 115:1). However, there is a halachic principle of Anan Sahadei (virtual witnesses), which means that if we know that something is occurring, our clear knowledge of this occurrence is the halachic equivalent of being witnesses to it. The heter of cholov stam, as formulated by Rav Moshe Feinstein (Igros Moshe YD 1:47-49), is predicated upon our clear knowledge that the government is properly regulating the dairy industry, including the government’s ensuring that milk from non-kosher species is not present. We know that the milk suppliers adhere to the dairy regulations because the suppliers are apprehensive of being penalized for violation and of their reputations being ruined through noncompliance. Halacha considers our clear knowledge that the milk is not from non-kosher species to be the equivalent of us being witnesses. Hence, the requirement that a Yisroel must witness all milking is fulfilled, as we are all deemed halachic witnesses to the milk’s production.

The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt”l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.