Shmini 5777: Ostrich Eggs and Miracle Meat

It might have been Parashat Shmini that put the idea of becoming a rabbi in my head. No, not the part about the two young priests getting zapped, but rather the detailed laws of kashrut. I grew up eating “glatt treife,” but by the time I was 13 I bought into the kashrut system as a way of cultivating self-control and awareness of the potential for holiness in every bite. I was one of the only teens who regularly attended services at Temple Emanuel in Woodcliff Lake, NJ (one of the others was named Benjamin Sommer), and somehow I got invited to make a presentation each week to the b’nai mitzvah. My presentations grew increasingly elaborate, no doubt trying the patience of our distinguished (and terse!) Rabbi Andre Ungar, reaching their apotheosis with an impassioned plea for kashrut one Shabbat morning. Weirdly, the congregation applauded, and my grandparents (who did not keep kosher, though Nana waited an hour to serve ice cream after eating meat) kvelled. Well, it took another decade to sort things out, but that is a decent origin story for my rabbinate.

And so it is to kashrut that we turn, but in a very strange way. The Torah’s code is reasonably specific about the criteria for kosher mammals and fish, but as for birds, all we get is a long list. What distinguishes the “impure” birds listed in Leviticus Chapter 11 (and Deut 14) from edible avians is not specified, though many have noted that the banned birds are all predators (yet I suppose that worms consider chickens to be predators). We can’t really say for sure what each listed species corresponds to in modern identifications—is a nesher really an eagle, or perhaps a vulture? (…”and I shall bring you on vultures wings” doesn’t have the same ring).

For today what really interests me is the ostrich, which is identified here as בת היענה. Literally, this could be read as “daughter of the ostrich,” though BDB suggests (p.419) perhaps “daughter of the desert or steppe.”  In other words, it is a bird that dwells in the desert, as ostriches tend to do. The rabbis, however, took its name literally and they asked, why does the Torah mention the ostrich’s offspring?

The issue is that bird eggs can get mixed up, and there is no way to know which bird laid which egg (especially since some birds take over the nests of others). And does it really matter in the end? If you want to eat an egg—it’s just an egg, not a full animal, so perhaps its species isn’t significant? Not so, say the rabbis (e.g. at Hullin 64b). The Torah mentions the “daughter” of the ostrich to teach us that not only is the ostrich is impure, but so too are its eggs, and by extension, so are the eggs of all non-kosher birds. And by extension from that, so too are all edible items produced by non-kosher animals (milk, skin etc.) considered to be non-kosher.

OK, fine, I hear you saying—I won’t eat an ostrich omelet, or drink a pig’s milk (is that even done?). What relevance does this have to me? As it happens, I am currently writing a teshuvah on the question of whether cultured (or lab-grown, or clean) meat can be made kosher. Cells are taken from a source animal and then cultured in a lab until muscle tissue is made—up to one trillion cells from the original source—and then turned into meat. There are many halakhic questions—given that the original cells are taken from a live animal, does this violate the ban on eating vivisectioned meat? Does that ban get inherited by distant descendants down the cell line? Another question—does the growth medium need to be kosher, or could non-kosher bovine fetal serum be used? After all, kosher fish like tuna frequently eat non-kosher fish in the sea. For that matter, vegetables are fertilized by the remains of non-kosher animals. Another question—if this meat is eventually brought to market, would it even be considered meat, or would it be pareve, like eggs? And finally, our question—does it really matter what kind of animal provides the original cells? After all, the final product will not be a cow or a pig, but just a matrix of muscle tissue that was cultured in a lab.

I’m still working it all out, but on the final question I think we have an answer. As Mishnah Bekhorot 1:2 teaches, שהיוצא מהטמא טמא והיוצא מן הטהור טהור, “That which emerges from the impure is impure, and that which emerges from the pure is pure.” So there will be no kosher pork chop. A kosher cheeseburger, however….just maybe. Come to the June CJLS meeting, and see what happens.



Deuteronomy 14:15 (cf. Levit. 11)

וְאֵת בַּת הַיַּעֲנָה וְאֶת הַתַּחְמָס וְאֶת הַשָּׁחַף וְאֶת הַנֵּץ לְמִינֵהוּ:

The ostrich, the nighthawk, the sea gull, and the hawk of any variety [may not be eaten].


Bavli Hullin 64b.

אמר חזקיה: מנין לביצת טמאה שהיא אסורה מן התורה? שנאמר: ואת בת היענה, וכי בת יש לה ליענה? אלא איזו זו ביצה טמאה.

Hezekiah says: what is the source that teaches that the egg of an impure bird is biblically forbidden? For it says: “and the daughter of the ostrich.” Does the ostrich have a daughter? Rather what is this—an impure egg.


Midrash Pesikta Zutrata to Shmini (31a):

ואת בת היענה. בת זו ביצת היענה. יצאת זו ללמד על כל הביצים של עופות הטמאים.

“And the daughter of the ostrich….” This “daughter” is the ostrich’s egg. This scriptural variant comes to teach about the eggs of all impure birds [are not kosher].


Mishnah Bekhorot 1:2

ומה הם באכילה? בהמה טהורה שילדה כמין בהמה טמאה מותר באכילה, וטמאה שילדה כמין בהמה טהורה אסור באכילה, שהיוצא מהטמא טמא והיוצא מן הטהור טהור.

What about for the purposes of eating? If a pure animal gives birth to one resembling an impure species, [the offspring] is permitted for eating. If an impure animal gives birth to one resembling a pure species, [the offspring] is forbidden for eating. That which emerges from the impure is impure, and that which emerges from the pure is pure.


Rambam, Laws of Forbidden Foods 3:1.

כל מאכל היוצא ממין מן המינין האסורין שלוקין על אכילתן הרי אותו המאכל אסור באכילה מן התורה, כגון חלב בהמה וחיה הטמאים וביצי עוף ודג הטמאים שנאמר ואת בת היענה זו ביצתה. והוא הדין לכל האסור כיענה ולכל הדברים הדומין לביצה.

Any food which emerges from one of the forbidden species that one is to be whipped for eating—this food is biblically forbidden to eat. For example: milk from impure impure domesticated and wild beasts, and eggs from impure birds and fish. For it says, “and the daughter of the ostrich”—this refers to its eggs. This rule applies to any [animal] that is forbidden like the ostrich, and for all things similar to eggs.