Does the hakpada of not having pas akum during the aseres y’mei yeshuva include that one should also not have chalav stam during this time, only chalav yisrael? What is the halacha? Thanks.
This is an interesting question, but for the sake of clarity you are asking about cholov stam and not about cholov akum, because cholov akum would is forbidden the whole year, and it isn’t a chumra.
In regarding to your question, although I have not seen anyone talk about it, it would make sense that one should be more makpid to eat only cholov yisroel during Aseres Yimei Teshuva. The reason is that during Aseres Yimei Teshuva we want to be extra careful about eating and doing things that might be assur, and even those who are not careful about pas yisroel during the rest of the year and to them it is permitted (because not all places accepted the gzeira, because it was difficult) however during this time we have to be careful. The poskim say that it is preferable to try to be more stringent and be mehader in halacha during these days.
Drinking cholov stam, according to many poskim is not permitted and even according to R’ Moshe who says that it is halachically permitted, he also says that one should preferably drink cholov Yisroel. Therefore it would seem that it is preferable to be makpid on cholov yisroel during Aseres Yimei Teshuva.
Regarding Aseres Yimei teshuva- Tur 603 from the Yerushalmi, Aruch Haswhulchan 603-2, Birkei Yosef 603- 1, Chayei Adom 143, Kovetz halachos fromR;’ S. Kaminetsky shlit”a on yomim Noraim chap. 22 ftnt. 3.
Regarding cholov stam see, Melamed L’hoyel Y.D. 33, Minchas Elazar 4:25, Zekan Aron 2:44, Emes L’Yaakov page 308, Minchas Yitzchok 1:138, 2:21, 10:31:15, Be’er Moshe 4:52, Teshuvos V’hanhugos 1:441, 2:373, Shevet Ha’Levi 4:87, Igros Moshe Y:D 1-49, 2 -31&35, 4-5, Chelkes Binyomin 115:16.