Genetically Engineered Fowl

By Rabbi Chaim Chazzan


What is the halacha if genes of a predatory bird (which is not kosher) were inserted into an egg of a chicken, causing the hatched chick to exhibit predatory tendencies although it looks exactly like a chicken, possessing all the signs of a kosher bird? Is it kosher?


In defining the kashrut of birds, the Torah lists all the non-kosher birds, but does not give us signs as to which birds are kosher, as it did with animals and fish. However the sages describe three physical signs shared by all kosher birds.

There is a debate amongst the rishonim if these signs can be relied upon to rule a bird as kosher, or is a mesorah is also necessary (a tradition that this bird was customarily eaten).  The ruling of the Shulchan Aruch and the Rema is (albeit with slight variances between them) that only species with a mesorah may be eaten.

However if a bird possesses the kosher signs but displays predatory tendencies, then even according to those who rely on the kosher signs some say it is forbidden. The Maharshal regards the predatory tendencies as an abnormality and therefore permits the bird. The Shach (as explained by meforshim) writes that we must be concerned that perhaps the kosher signs are the irregularity, but truly the bird is not kosher.

In our case where we can attribute the predatory tendencies to the genes that were inserted, there is no reason for concern. Therefore it is possible that all poskim would agree that we deem the bird as kosher, and that its predator traits are abnormal. However in practice it is proper to refrain from eating such a bird, since we find that the Rema was very stringent concerning the kashrut of birds.

משנה חולין דף נט ובגמ’ דף סג, רמב”ם הל’ מאכלות אסורות פ”א הי”ד, טור יו”ד סי’ פב בשם רש”י, ים של שלמה חולין פ”ג סי’ קטו, שו”ע יו”ד סי’ פב וש”ך ס”ק ח,’ שו”ת משיב בהלכה יו”ד סי’ ח

Reprinted with permission from  Lmaan Yishmeu – a project of Mercaz Anash. To see more articles visit 

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