I heard in a recent shiur that Dayan Weiss zatzal ruled that an animal that delivered its young via caesarean section is considered a treife. Therefore its milk cannot be drunk. When supervising milking the shomer checks that any such animals are locked away before milking.

How do those those who permit cholov akum put up with this possibility? Is it through bitul?

  • 2
    (Live cattle are never Batel.) There's always some number of Treif animals in a given herd, so I don't see why this issue changes anything. How do you ever drink milk without slaughtering the animal and checking all 36 possible Treifot?
    – Double AA
    Commented Jan 23, 2018 at 16:46
  • 3
    @DoubleAA Is there not a difference between an identifiable tereifa and a possible but unidentifiable tereifa? Commented Jan 23, 2018 at 20:38
  • Comments are not for extended discussion; this conversation has been moved to chat. Commented Jan 25, 2018 at 2:34
  • @Yez no treifa is unidentifiable. The case of chalav akum is a case where no one checked and now we have the milk. Seems exactly the same.
    – Double AA
    Commented Feb 21, 2018 at 0:47
  • @DoubleAA While the animal is alive? Commented Feb 21, 2018 at 0:48

4 Answers 4


R Asher Weiss has a teshuva on a similar topic (Shut Minchat Asher, vol. 1, page 126). He answers how one can drink milk from a herd when one knows statistically some of the cows will be tereifot.

He explains that as long as the majority of the cows are kosher, the statistics of what percentage are really tereifot don't matter. Specifically he writes that even if it is true that from a statistical probability it is impossible to say that all cows in a herd are kosher, we can rely on the concept that this herd follows the general statistics of the average number of tereifot in a herd. From a din Torah perspective, every cow has the presumption of being kosher (since statistically more than 50% have been found to be kosher), thus even when bringing many of these cows together, they are all kosher from a Torah perspective.

I see now that Halachipedia mentions a similar argument but see there for other arguments.

Rav Asher Weiss (Minchat Asher Shemot siman 43) argues that principally we view each cow as kosher because of kol d’parish m’ruba parish and even when their milk is mixed up the milk from each cow retains its kosher status despite the overall statistic. His primary argument is that once we have a halachic principle to state that the milk is kosher the halacha ignores the physical reality or statistic. One proof for his argument can be derived from Gemara Zevachim 73b which implies that once the principle kol d’parish m’ruba parish is employed even if the items are later mixed up, the remain kosher. Another proof is the Rama who states that the cheese made from many unchecked cows who were only considered kosher by merit of a chazaka remains kosher. This gemara is cited by the Rosh (Chullin 7:37) for a similar point.

I also see R Michoel Zylberman from YU's Kollel wrote an entire article on the topic in the Journal of Halacha bringing different proofs and concluding with the reasoning above. See especially pp. 106 and following.

  • "when one knows statistically some of the cows will be tereifot" That's not exactly the question here. The question here is where we know certain identifiable cows are treif, not just that statistically there is very likely a non-zero number of treif cows.
    – Double AA
    Commented Jun 13, 2021 at 14:15
  • I don't think this is correct. The question states "How do those those who permit cholov akum put up with this possibility?" In other words we have a herd with a possibility some cows might be treifot. Or do you read it differently? See your first comment below the question.
    – mbloch
    Commented Jun 13, 2021 at 14:30
  • The question is about herds with identifiable treifot, not just statistically likely treifot. I'm not convinced there is a halachic difference but those are the facts.
    – Double AA
    Commented Jun 13, 2021 at 14:40
  • I see. You read the title. I read the body of the question which speaks of herds with the possibility of a tereifa because of caesarean section. I also don't believe there is a difference in the answer
    – mbloch
    Commented Jun 13, 2021 at 14:48

I'm not sure that all Cholov Yisrael dairy producers do this; there have been a number of questions in the past about whether many dairy cows are treifa.

In a theoretical sense, we know that some dairy cows -- let's say more than 1.6% but less than 50% -- are treifos. If I have one cow on my farm, Bessie, then rov says assume Bessie is kosher, so Bessie's milk is 100% kosher. Okay I walk into a modern dairy setup with a thousand cows' milk all mixed together; if 4% of those cows are treifa, does that mean my milk is 4% treifa and 96% kosher? If so it's not kosher! Rabbi J. David Bleich writes about this in Tradition Spring 2008. The answer seems to be based on a ruba de-leisa kaman. If I don't know that any particular cow on my farm is treifa, even if I know that the general population in theory has a 4% treifa rate, then I assume each of my cows is 100% kosher, and thus the milk is 100% kosher.

So your question would only be if a mashgiach walks onto a dairy farm and knows specifically that there are one or more treifa cows here. Which I doubt is usually the case in industrial-scale chalav stam production.

  • 2
    The question isn't about a mashgiach. It's about where there is no mashgiach.
    – Double AA
    Commented Feb 21, 2018 at 0:56
  • A mixture is ruba deyta kaman
    – kouty
    Commented Apr 18, 2019 at 19:26

From the Chashash Terefa point of view, the unsupervised milk is better. Because nobody would try to check if a cow is Terefa. Even if they decide to eat it, the non Jews would not verify if the animal is terefa. So we have both Chazaka and Rov.

  1. The first is Chazaka, Milk cows are greater than one year, so they wasn't terefot when they born. The chazaka is a Chazaka demeYkara. This point is a Machloket Rishonim in Gemara Chulin 11a. See Tosfot paragraph Atia. Tosfot rules that this Chazaka is not valid because the non-terefut was not clear at time. We know that the cow wasn't terefa before 12 month because a terefa cannot live 12 months.

  2. Even if the Chazaka per se is not valid, we have a Rov. Most animals are healthy. Moreover, Rav Shimshon bar Shimshon says there is a Chazaka that come from the strength of Rov (he think that Rov is a Berur equivalent). That is, even if a cow becomes Terefa and you have cheese from it, Rashba (there) says that from the strength of the Chazaka we say that it became terefa after the confection of the cheese.

Anyways, in non supervised dairy, there is no case of discovery of Terefa. Even more, if it was the case, milks of all cows are mixed and Zil batar Ruba, the mixture of Chalav Terefa with a majority of Chalav not Terefa is cancelled.


See also this article from OU Kosher Milk from a Possibly Treif Cow

Halacha states that milk from a tereifah animal – meaning an animal which suffers from a mortal wound, as understood by Chazal – is non-kosher. (Shulchan Aruch, Yoreh Deah 81:1) This prompts a good question: How can one know whether or not the milk he consumes is from a tereifah cow?

The OU Kosher article includes the following:

There is a rule that “Kol d’parish mi-ruba parish” – “Anything that separates out (of a series of sources among which the minority are not kosher) is governed by the status of the majority”.


The Shulchan Aruch and Remo (ibid.) rule otherwise, stating that a mixture of milk from one known tereifah animal and a herd of 60 cows that are assumed to be kosher is permissible; we do not treat the mixture as containing additional tereifah milk from the likely additional percentage of tereifos in the herd.

  • why is a cow in a herd considerd Parish? I am assuming they are all together in one spot when they get milked
    – Yoreinu
    Commented Jun 18 at 15:25
  • @Yoreinu please refer to the article at oukosher.org/blog/consumer-kosher/…
    – Edward B
    Commented Jun 18 at 15:29

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .