Buffalo Burgers and the Zebu Controversy
Parashas Shemini discusses and specifies the requirements and parameters for determining the kosher status of members of the animal kingdom. For example:
- Fish need to have fins and scales; while
- Domestic land animals (beheimos) must chew their cud (ruminant) and have completely split hooves;
- Non-domestic land animals (chayos) share the same basic set of rules to be considered kosher, but have slightly differing halachos. Some of the more well-known ones include that they do not have the prohibition of eating forbidden fats (cheilev) that a domestic land animal does, but there is a requirement to cover its blood immediately after slaughtering (kisui hadam), similar to a fowl but unlike a beheimah.
Our question is what a buffalo is considered. Can we partake of a nice juicy buffalo burger? Although the Shulchan Aruch himself rules that a buffalo is considered a kosher beheimah, it is quite certain that he was not referring to our American Buffalo - which was unknown at the time and is truly a Bison - but rather the Asian Water Buffalo.
Still, it is clear that the American Buffalo / Bison chews its cud and has split hooves, the signs of a kosher animal. Surely that should be enough to let us start grilling!
But, if so, why is its meat not more common? And, on an anecdotal level, this author has never seen Buffalo (Bison) Burgers advertised in Eretz Yisrael in any Mehadrin supermarket, butcher, or even fast food joint! So, as the expression goes, “Where’s the beef?”
Cryptic Comments and Fowl Play
The reason for the lack of American Buffalo (Bison) meat is based on a cryptic comment of the Shach, where he compares the kashrus status of the chaya to that of fowl.
The Torah enumerates 24 various non-kosher “birds”. Since so many thousands of avian species exist, Chazal specify four necessary anatomical indicative features (simanim) that identify a specific type of fowl as kosher: an extra toe, a crop, a peelable gizzard (meaning the gizzard’s inner lining can be peeled from the outer muscle wall), and being non-predatory (‘doreis’).
However, as the exact translation of the non-kosher birds listed in the Torah is unknown, as well as the fact that we cannot be assured of the absolute non-predatory nature of any given species of bird, many early authorities contend that we do not rely on our understanding of these simanim, but rather only eat fowl that we have a tradition (mesorah) that this specific species is indeed kosher. Indeed, Rashi cites precedent from the case of the ‘Swamp Chicken’ (Tarnegolta D’Agma), with which even Chazal made a mistake, not realizing at first that it is truly predatory in nature (doreis) and therefore non-kosher. He therefore maintains that since we are not experts, we additionally need a mesorah to allow fowl to be eaten. The Rema in fact, and concurred by virtually all halachic authorities, definitively rules this way lemaaseh, that we may not eat any species of bird without a mesorah.
Concerning the laws of a kosher chaya, the Shulchan Aruch discusses the different types of horns which distinguish a chaya from abeheimah. The Shach enigmatically comments that “I did not elaborate, since nowadays we only use what we received as a mesorah, similar to the laws of kosher fowl”. The basic understanding seems to be that the Shach is implying that just as for a bird to be considered kosher it needs to have a mesorah even if it fits all other requirements, so too a chaya would also need to have a mesorah to allow it to be eaten, even though it is technically kosher! This would imply that the American Bison would be on the verboten list, as if it was an unknown animal, by definition it could not have had a mesorah.
The Pri Megadim, foremost commentary on the Shach, categorically rejects such a possibility, as it would run counter to the Gemara’s ruling that identifying features are sufficient to determine a chaya’s kashrus status. Additionally, there is no mention of such a requirement in any of the early authorities. He concludes that the Shach must have meant something else entirely; namely regarding the differences between a beheimah and a chaya: Since the defining distinctions between a beheimah and a chaya are often unclear, one should not eat the cheilev of any species (permissible by a chaya, prohibited by a beheimah) unless we have an oral tradition that said species is indeed a kosher chaya. In other words, the Shach was referring to the need of a mesorah to allow a nuance in halacha, but not in actually identifying a kosher animal. The majority of later authorities agree with the Pri Megadim’s understanding of the Shach’s comment and rule likewise, that mesorah plays no factor in whether or not an animal (domestic or not) may be eaten; the only necessary requirements being that it chews its cud and has split hooves. This would mean that buffalo burgers can be on the menu!
However, before you get that grill fired up, you might want to “Hold Your Horses (er… Buffalo)”. Two major later authorities, the Chochmas Adam and the Aruch Hashulchan both seem to accept the Shach’s words at face value, and not like the Pri Megadim’s interpretation, implying that an oral tradition is needed to allow any land animal to be eaten. In fact, the renowned Chazon Ish ruled this way explicitly in 1950, regarding the importing of the Zebu (“The Indian Humpbacked Cow”) to Israel, stating that the Chochmas Adam’s interpretation of the Shach’s comment is the correct one! He therefore maintained that any “new” land animal may not be eaten unless there is a mesorah. He added that since the sefer Chochmas Adam was considered in Lithuania (Lita) as the authoritative work on Yoreh Deah, we must follow his ruling relating to this. The Chazon Ish concludes that the only known animals that we eat are “cows, sheep, and goats”. This understanding would obviously not permit the Buffalo / Bison either.
In fact when the “New Zebu Controversy” broke out in 2004, many wished to have Zebu meat banned (which would logically be extended to buffalo as well), based primarily on the Chazon Ish’s strongly worded ruling from over 50 years prior.
Grounds for Leniency
However, several contemporary authorities pointed out many potential flaws with making such an argument, including:
- If the Shach truly meant to qualify the permissibility of eating a chaya, he would have written it in the previous chapter (Y.D. 79), which discusses which animals are kosher, and not where he actually commented, where only identifying features were being discussed.
- The Chochmas Adam and Aruch Hashulchan are not really any clearer in his ruling than the Shach himself; thus allowing their comments to be interpreted like the Pri Megadim’s opinion as well.
- The Chazon Ish himself only restricted an animal that is considered a “new species”; it has since been proven that the Zebu has been eaten and considered kosher for a long time in many different countries. In fact, due to this reasoning, the Chazon Ish himself ate turkey, the quintessential ‘New World’ fowl, based on a responsum of his father’s, Rav Shemaryahu Yosef Karelitz.
- Rav Yaakov Kamenetzky has been quoted as maintaining that the Pri Megadim was considered the authoritative work in Lita, and not necessarily the Chochmas Adam.
- Even if we would assume that the Chochmas Adam’s ruling would be binding for those in Lita, it most definitely would not be obligatory to any other communities, who would be free to follow their own halachic authorities.
- The Chochmas Adam himself writes that deer (venison) is permissible, and as mentioned previously, the Shulchan Aruch ruled that Water Buffalo is kosher, proving that the Chazon Ish’s rule of only eating “cows, sheep, and goats”, is not absolute.
- The Chochmas Adam and the Aruch Hashulchan both wrote explicitly that only a chaya needs a mesorah, not a beheimah. The Zebu (being a humpbacked cow) however, is considered a beheimah, not a chaya, and therefore should not require an oral tradition.
- The Chazon Ish himself, in a later letter, accepts that the Zebu is technically a kosher animal, but reiterates that we need to have a proper mesorah to permit it to be eaten. Yet, he concludes that “in our times, with Reform making inroads into authentic Torah Judaism, it is impossible to allow new things to be considered permitted if in the past they were deemed prohibited... as one breach (of tradition) leads to subsequent breaches”. Nowadays, it can be debated that this logic might no longer be applicable.
Buffalo To Go?
Due to these rationales, as well as the facts that currently most milk cows in Israel are descended from Zebu, and that many Tefillin and Sifrei Torah are written on parchment (klaf) made from their hides, and although initially reported otherwise, Rav Yosef Shalom Elyashiv zt”l, and other contemporary poskim, later concluded that these humpbacked cows are essentially permitted.
Therefore, even if one wishes to be stringent with eating the Zebu or Buffalo itself (as Rav Elyashiv himself favored), nevertheless, regarding potential related offshoot issues, such as crossbred offspring and the halachic status of their milk, as well as Sifrei Torah and Mezuzos written on their hides, etc. the final psak is that these are certainly permitted.
All this said, are we going to see Buffalo Burgers or ‘Zebu Zurprize’ in our local supermarket any time soon? In America, perhaps. In Israel, probably not.
As even though many contemporary authorities rule that there is no real kashrus issue with them and that they may be eaten by even those stringent on the highest levels of kashrus, on the other hand, authorities maintain that out of respect and in deference to the great Chazon Ish, and especially in Eretz Yisrael, “the land of the Chazon Ish”, it is preferable to abstain from partaking of them. For this reason Buffalo / Bison Burgers apparently won’t be found in Israel with a Mehadrin hashgacha, although more easily obtainable in the land “where the buffalo roam”.
This article was written L’Iluy Nishmas Yisrael Eliezer ben Zev a"h - my dear Great-Uncle Larry Spitz, who was niftar this month, L’Zechus for Shira Yaffa bas Rochel Miriam v’chol yotzei chalatzeha for a yeshua teikif umiyad, and l’Refuah Sheleimah for Shoshana Leah bas Dreiza Liba, Mordechai ben Sarah, and Shayna bas Fayga.
Rabbi Yehuda Spitz, author of M’Shulchan Yehuda on Inyanei Halacha, serves as the Sho’el U’Meishiv and Rosh Chabura of the Ohr Lagolah Halacha Kollel at Yeshivas Ohr Somayach in Yerushalayim. He also writes the ‘Insights Into Halacha’ column for Ohr Somayach’s website: https://ohr.edu/this_week/insights_into_halacha/.
For any questions, comments or for the full Mareh Mekomos / sources, please email the author: firstname.lastname@example.org.
 Vayikra (Parashas Shemini Ch.11: 9 - 13). The specifics of defining and discerning which animals are considered kosher are also presented in Parashas Re’eh (Devarim Ch. 14: 9 - 10). This topic is discussed at length in a previous article titled “Fish With Legs?!”.
 Vayikra (Parashas Shemini Ch. 11: 1 - 3) and Devarim (Parashas Re’eh Ch. 14: 6).
 See Vayikra (Parashas Acharei Mos Ch. 17: 13 and Mishnah and Gemara Chullin (83b and 89b).
 Shulchan Aruch (Y.D. 28: 4). The Rema (ad loc.) however, is unsure and classifies it as a possible chaya. The main difference between these two positions is whether one should cover its blood after slaughter without a bracha.
 The Ba’er HaGolah (ad loc. 9) traces this to the Agur (1099), citing Rav Yeshaya Ha’acharon of Italy. This buffalo is also mentioned by Tosafos (Zevachim 113b s.v. orzulaya), the Mordechai (Chullin 653), the Shach (Y.D. 80: 3), and Aruch Hashulchan (Y.D. 80: 12). In Italy “buffalo” is still used to refer to the Water Buffalo. It would be hard to imagine that these early authorities were referring to the American Bison which was completely unknown at the time of writing their sefarim. See Rabbi Dr. Ari Z. Zivotofsky’s excellent article on www.kashrut.com titled “Kashrut of Exotic Animals: The Buffalo.” Rav Shlomo Miller of Toronto, in his second teshuva on topic (titled ‘Zebu and Bison 2’; available on his Kollel’s website - www.kollel.org), maintains that as we are uncertain whether Bison is abeheimah or chaya (or possibly the fabled koy or kviy), even if one holds that it is permitted to be eaten, it nonetheless requires kisui hadam and it may not be bred.
 Vayikra (Parashas Shemini Ch. 11: 13 - 24) and Devarim (Parashas Re’eh Ch. 14: 11 - 21).
 Mishnah and following Gemara (Chullin 59a - 61b). There is much debate among the Rishonim how to properly define these simanim, especially a ‘non-doreis’, as well as if the Gemara’s intent was that all four features are necessary to render a bird kosher, or if the three physical characteristics are sufficient proof that the fowl is non-predatory and therefore kosher.
 Gemara Chullin (62b) and Rashi (ad loc. s.v. chazyuha).
 Rema (Y.D. 82: 3). The Shulchan Aruch (Y.D. 82: 2) actually rules this way as well, but allows several more leniencies (see ad loc. 82: 3) than the Rema’s stronger language.
 Shulchan Aruch (Y.D. 80: 1). Speaking of horns, for a fascinating discussion of what a unicorn might be considered, see Pri Chodosh (Y.D. 80: 2) and Shu”t Beis Yaakov (41).
 Shach (Y.D. 80: 1). See also the Ibn Ezra’s commentary to Parashas Re’eh (Devarim Ch. 14: 5) who likewise writes an ambiguous comment related to beheimos and chayos which can also possibly be interpreted in both of these different manners. It is noteworthy that Rav Yisroel Halevi Belsky (Shu”t Shulchan Halevi, Ch. 19: 1 s.v. u’mah) writes that it is abundantly clear that the Ibn Ezra did not intend to get involved in the practical halacha of defining said animals, but is rather simply stating that he is aware that there are other kosher animals extant, yet is uncertain how to properly identify them. In other words, he is merely pointing out that these other animals were not common in his time and place (1100s, Spain).
 Pri Megadim (Y.D. 80: S.D. 1).
 Gemara Chullin (59b).
 Including the Kreisi U’Pleisi (ad loc. 2), Pischei Teshuva (ad loc. end 1; he is arguing on the Beis Yaakov ibid. s.v. v’gam, who opines that a chaya must have another siman in order to be considered kosher: horns; the Beis Yaakov’s opinion is rejected by many, if not all, halachic authorities), Beis Yitzchak (ad loc.Amudei Zahav 3), Mishmeres Shalom (ad loc. S.D. 1), Darchei Teshuva (ad loc. 3), and Kaf Hachaim (ad loc. 5).
 Chochmas Adam (36: 1) and Aruch Hashulchan (Y.D. 80: end 10).
 Chazon Ish (Y.D. 11: 4 and 5), Kovetz Igros Chazon Ish (vol. 1: 99; vol. 2: 83; and vol. 3: 113). These writings of the Chazon Ish were actually a series of correspondence between himself and the Chief Rabbi of Israel, Rav Yitzchak Isaac Halevi Herzog. Rav Herzog wrote a Kuntress on the topic, titled ‘Kuntress Pnei Shor’ (printed in his responsa as Shu”t Heichal Yitzchak Y.D. vol. 1: 20) concluding that the Zebu is permitted to be eaten. He also maintained that there was a mesorah in India and other countries going back centuries that the Zebu was considered a kosher cow. He suggests that anyone who argues that a mesorah is required is possibly violating the Biblical prohibition of ‘Bal Tosif’, adding on to the Torah’s commandments (Devarim, Parashas Re’eh Ch. 13: 1; see Sefer Hachinuch ad loc. Mitzva 454). See also Pe’er Hador (of the Chazon Ish; vol. 4, pg. 226 - 230), and Orchos Rabbeinu (new edition; vol. 4, pg. 9 - 16), which cite and summarize the correspondence. Rav Chaim Kanievsky was recently quoted (sefer Doleh U’Mashkeh pg. 255 - 256) regarding the ‘Bor Hahodu Shehaya B’zman HaChazon Ish’, as expressing very strongly that he considers it 100% non-kosher. The Beis Halevi is quoted as being of the same opinion as the Chazon Ish - see Contemporary Halakhic Problems (vol. 5, pg. 255, footnote 15).
 The Chazon Ish’s brother-in-law, the Steipler Gaon (see Orchos Rabbeinu; new edition, vol. 4, pg. 91: 20) also held this way, that Rav Avraham Danzig’s classic halachic works, Chayei Adam on Orach Chaim and Chochmas Adam on Yoreh Deah were ‘sifrei yesod lehoraasav v’hanhagosav’. His son, Rav Chaim Kanievsky, follows this as well, telling people who were nichshal in a Bassar B’Chalav matter, to relearn and review the halachos with the Chochmas Adam. See sefer Doleh U’Mashkeh (pg. 258 - 259) and Rabbi Yaakov Skoczylas’ Ohel Yaakov (on Issur V’Hetter, revised edition pg. 222, footnote s.v. v'shamaati).
 See Orchos Rabbeinu (new edition; vol. 4, pg. 9 - 16) at length. Likewise, Rav Shlomo Miller wrote a strongly worded teshuva on topic dated 8 Shevat 5766 (titled ‘Zebu and Bison’; available on his Kollel’s website - www.kollel.org) stating that although there are kashrus agencies who grant hashgacha to Zebu and / or Bison meat, nevertheless the psak of the Chazon Ish was already accepted, and based on this, Rav Elyashiv and other poskim of Eretz Yisrael prohibited this meat, and therefore it should not be eaten. However, in a later (albeit undated) teshuva on topic (titled ‘Zebu and Bison 2’; also available on his Kollel’s website) and possibly due to the arguments raised above, Rav Miller backtracks somewhat on his prohibitory psak, writing that his intention is simply to raise awareness for those who follow the Chazon Ish, that nowadays they should not eat Zebu and Bison, as the same issues should still apply.
 Including Rav Yitzchak Isaac Halevi Herzog (ibid.), Rav Meshulem Roth (‘The Hordonka Iluy’; Shu”t Kol Mevasser vol. 1: 9), Rav Shalom Krauss (Shu”t Divrei Shalom vol. 7: 38), Rav Shmuel Halevi Wosner (Shu”t Shevet Halevi vol. 10: 114), Rav Yisroel Halevi Belsky (Shu”t Shulchan HaLevi, Chelek HaBiurim 19), Rav Yechezkel Roth (Shu”t Eimek HaTeshuva vol. 6: 305), and Rav Asher Weiss (Minchas Asher al HaTorah, Shemini, 14). Although not all bring the same arguments, nevertheless, each of these authorities cites at least one of these reasons. This was also the opinion of Rav Moshe Feinstein (see Mesores Moshe vol. 1, Y.D. 13, pg. 211 and footnote 22, and vol. 2, Y.D. 15, pg. 169), that the ikar is to follow the Pri Megadim’s understanding and that buffalo is a kosher animal. See also Rabbi Dr. Ari Z. Zivotofsky’s article on topic published in Kovetz HaMe’ayen (Teves 5768, vol. 48: 2, pg. 16 - 18).
 See for example, the Beis Yitzchak (ibid.) and Kaf Hachaim (ibid.), who cite their opinions this way as basic understanding.
 See Shu”t Meishiv Davar (Y.D. 22). Although referring to the turkey, the symbolic New World fowl which the vast majority of world Jewry eats, even though a mesorah pre-Columbus would be a seeming impossibility, nonetheless, the Netziv permits it to be eaten on this basis, that it has been eaten for a long time and is now considered having a mesorah. For more on the topic of the kashrus status of turkey, and its more kashrus-wise complicated companion fowl, the Muscovy Duck, Posen Hen, Guineafowl, and / or Cochin, and how they are / were viewed from a halachic perspective through the ages, see Nachal Eshkol (on the Sefer HaEshkol, Hilchos Beheima, Chaya, v’Of 22: 10; he understands there to be an Indian mesorah on the turkey), Knesses HaGedolah (Y.D. 82: 31), Shu”t Shoel U’Meishiv (Mahadura Telita’ah vol. 1: 149 and Mahadura Chamisha’ah vol. 1: 69), Shu”t Chasam Sofer (Y.D. 74), Shu”t Divrei Chaim (O.C. 9 and Y.D. vol. 2, 45 - 48), Shu”t Maharam Schick (Y.D. 98 - 100), Shu”t Tuv Ta’am V’Daas (Mahadura Telita’ah 150 - 152), Shu”t HaElef Lecha Shlomo (Y.D. 111), Shu”t Beis Yitzchak (Y.D. vol. 1: 106), Shu”t Yehuda Yaaleh (vol. 1, Y.D. 92 - 94), Shu”t Tzelosa D’Avraham (7), Shu”t HaRim (Y.D. 8), Shu”t Tzemach Tzedek (Y.D. 60), Shu”t She’eilas Shalom (Y.D. 22), Arugas Habosem (Kuntress HaTeshuvos 16), Shu”t Ori V’Yishi (vol. 1: 11), Damesek Eliezer (51: 84 and Ch. 4, 12: 73), Shu”t Binyan Tzion (vol. 1: 42), Shu”t Dvar Halacha (53), Rav Yissachar Dov Illowy’s Shu”t Milchemos Elokim (pg. 162 - 165; also citing teshuvos from Rav Samson Raphael Hirsch and Rav Nosson Adler, the first Chief Rabbi of England - regarding the Muscovy Duck), Shu”t Avnei Nezer (Y.D. 75), Shu”t Michtav Sofer (Y.D. 3), Shu”t Melamed L’hoyeel (vol. 2 - Y.D. 15), the Maharsham’s Daas Torah (Y.D. 82: 3), Shu”t Mei Ba’er (19; who opines that the turkey actually came from India and even has a mesorah dating back to Moshe Rabbeinu!!), Zivchei Tzedek (82: 17), Darchei Teshuva (82: 26), Rav Yehuda Leib Tzirelsohn’s Ma’archei Lev (Chelek HaTeshuvos, Y.D. 30 - regarding the Posen Hen), Shu”t Divrei Malkiel (vol. 4: 56), Rav Yosef Aharon Teren of Argentina’s Zecher Yosef (pg. 1a - 6b; regarding the Muscovy Duck), Shu”t Nishmas Chaim (Y.D. 63), Kaf Hachaim (Y.D. 82: 21), Shu”t Igros Moshe (Y.D. vol. 1: 34; also citing the opinions of Rav Naftali Carlebach and Rav Yosef Eliyahu Henkin - regarding the Posen Hen), Shu”t Har Tzvi (Y.D. 75 - regarding the Muscovy Duck), Shu”t Minchas Yitzchak (vol. 5: 31), Kovetz Mesorah (vol. 3, pg. 60 - 65; in a maamar from the Beis Avi, Rav Yitzchak Isaac Liebes, regarding Rock Cornish Hens), Shu”t Shulchan Halevi (Ch. 19: 1), Rav Shmuel Salant’s posthumously published Aderes Shmuel (222; pg. 225 - 228), Sichas Chullin (pg. 429, on Chullin 63a; who astoundingly posits that the turkey mesorah possibly came from the Ten Lost Tribes who might have been early American Natives, as per Rav Menashe ben Yisrael’s unsubstantiated theory, who then contacted Indian and English Poskim!!), and Rav Yaakov Yedidyah Adani’s fascinating halachic history of the Muscovy Duck, published in Kovetz Eitz Chaim (vol. 26; Elul 5776, pg. 430 - 455). Additionally, and quite interestingly, we find that several Acharonim, including the Bach (O.C. 79, s.v. kasav B”Y), Magen Avraham (ad loc. 14), Ateres Zekeinim (ad loc.), Ba’er Heitiv (ad loc. 12), Aruch Hashulchan (ad loc. 16), and Mishnah Berurah (ad loc. 26), understand the Yerushalmi’s (Eruvin Ch. 3, Halacha 5) ‘Red Chickens’ (Tarnegolim Aduma), which we must distance ourselves from its excrement while davening (see Shulchan Aruch ad loc. 6; as opposed to the understanding of red excrement from a chicken), to be referring to a turkey; giving implicit consent that it is indeed a kosher bird (however, and quite interestingly, it remains unclear how an American New World fowl was seemingly extant in Eretz Yisrael at the time of the writing of the Yerushalmi). In fact, the Chazon Ish himself ate turkey, based on a teshuva of his father’s, Rav Shemaryahu Yosef Karelitz [this teshuva was recently published in Shu”t V’Chiddushim Chazon Ish (132)]. See Orchos Rabbeinu (new edition; vol. 4, pg. 9: 1). The mainstream opinion that turkey is considered an acceptable fowl is also seen by the contemporary Poskim who allowed it being eaten on Thanksgiving. This issue was discussed at length in a recent article titled ‘Thanksgiving: Harmless Holiday or Chukos HaGoyim?’.
 Shu”t Shulchan Halevi (ibid., pg. 282, s.v. v’yoser).
 Printed in Pa’er Hador (ibid, pg. 228 - 230), and later reprinted in Kovetz Igros Chazon Ish (vol. 3: 113), and Orchos Rabbeinu (ibid, pg. 12 - 13).
 It is worthwhile to note that another of the issues the Chazon Ish prohibits for the same reason is slaughtering meat in another country and importing it to Eretz Yisrael. This author is not entirely sure why that proviso is widely ignored (as even the most Mehudar Badatzim perform shechitah in foreign countries), but the Zebu issue erupted in renewed controversy, even as both are part and parcel of the same letter the great Chazon Ish wrote.
 ‘Hoda’ah L’Tzibbur’, B’sheim Rav Elyashiv and Rav Nissim Karelitz, dated 21 Adar 5764 – interestingly signed by three ‘Talmidim’ - Rav Yitzchak Mordechai Rubin, Rav Dovid Aryeh Morgenstern, and Rav Moshe Mordechai Karp, and not Rav Elyashiv himself; originally published in the Israeli daily Yated Ne’man newspaper on March 19, 2004. See Orchos Rabbeinu (ibid.), Kovetz Yeshurun (vol. 22, pg. 934 s.v. uv”g), Rav Shlomo Miller’s first teshuva on topic (ibid.), Contemporary Halakhic Problems (vol. 5, pg. 260), Rav Yirmiyohu Kaganoff’s recent From Buffalo Burgers to Monetary Mysteries (pg. 217 - 218, “Anyone For a Buffalo Burger?”), and Halachic World (vol. 2, pg. 162, “Bison Blues”).
 See Shu”t Shulchan Halevi (ibid, pg. 284: 2), Minchas Asher (ibid, pg. 82, s.v. hinei), Rav Shlomo Miller’s second teshuva on topic (titled ‘Zebu and Bison 2’), and Shu”t Videbarta Bam (vol. 2: 235 and 236 s.v. v’shamaati; citing Rav Dovid Feinstein). This is because although these animals may not have a true mesorah, and according to some, may therefore not be eaten, nonetheless, they still have simanei kashrus, and are therefore definitively considered kosher animals. As such, the potential problematic issues with their offspring regarding ‘Zera HaAv’ (GemaraChullin 79a) should not apply in our case, as there is a Safek Derabbanan on a disputed prohibition that is clearly at worst, a minhag. [See Gemara Bechoros (7a), Rambam (Hilchos Maachalos Asuros Ch. 1: 13), Lechem Mishnah (ad loc.), Tosafos (Chullin 58a s.v. m’kaan), and Shu”t Avnei Nezer (Y.D. 75: 8).] See also Orchos Rabbeinu (ibid.) which details several fascinating conversations between its author, Rav Avrohom Halevi Hurvitz and Rav Ezriel Auerbach, Rav Elyashiv’s son-in-law, on this topic. He concludes that lemaaseh, Rav Elyashiv held that the Israeli hashgachos should not perform shechitah on Zebu to import it davka to Eretz Yisrael, as the ikar hanhagah should be according to “Rabban shel Yisrael” the Chazon Ish, but even so, notes that Rav Elyashiv held that the Chazon Ish’s psak is not the “psak hakavua b’davar issur achilas beheimos bli mesores”, and therefore was essentially meikil regarding other Zebu-related issues, such as chashashos of offspring, milk, Sifrei Torah andTefillin, etc.
 See Shu”t Shevet Halevi (ibid.), Orchos Rabbeinu (ibid.), Minchas Asher (ibid.), and Shu”t Videbarta Bam (ibid., citing Rav Dovid Feinstein).