יורה דעה שט״זYoreh De'ah 316

Se’if 1א׳

הַלּוֹקֵחַ בְּהֵמָה מֵהָעוֹבֵד כּוֹכָבִים, וְאֵין יָדוּעַ אִם בִּכְּרָה וְיָלְדָה, הֲרֵי זֶה סְפֵק בְּכוֹר, וְיֵאָכֵל בְּמוּמוֹ לַבְּעָלִים, וְאֵינוֹ לַכֹּהֵן, שֶׁהַמּוֹצִיא מֵחֲבֵרוֹ עָלָיו הָרְאָיָה. בֵּין אִם לְקָחָהּ תּוֹךְ שָׁנְתָה, אוֹ אַחַר שְׁנָתָהּ, וַאֲפִלּוּ אִם הָעוֹבֵד כּוֹכָבִים מֵסִיחַ לְפִי תֻּמּוֹ שֶׁכְּבָר בִּכְּרָה, אֵינוֹ נֶאֱמָן. וְסִימָנִים שֶׁבְּחִדְקֵי קַרְנֶיהָ אֵין מַעֲלֶה וְלֹא מוֹרִיד לִסְמֹךְ עֲלֵיהֶם (הַגָּהוֹת מָרְדְּכַי פ' הָאִשָּׁה).

One who buys an animal from an idolater, and it is not known whether she has already borne her first, this is a doubtful firstborn, and it is eaten in its blemish by the owners, and it is not the priest's, for the burden of proof lies on the one who seeks to take from his fellow. Whether he bought her within her year or after her year; and even if the idolater speaks in his innocence (mesiach lefi tumo — one who tells of a thing in passing, with no thought of giving testimony) that she has already borne her first, he is not believed. And the signs in the rings of her horns neither raise up nor bring down as grounds to rely on (Hagahot Mordechai, chapter "The woman").

Se’if 2ב׳

לָקַח בְּהֵמָה מֵינִיקָה מֵהָעוֹבֵד כּוֹכָבִים, אֵינוֹ חוֹשֵׁשׁ שֶׁמָּא בְּנָהּ שֶׁל אַחֶרֶת הִיא מֵינִיקָה, אֶלָּא הֲרֵי זוֹ בְּחֶזְקָת שֶׁיָּלְדָה. וַאֲפִלּוּ הָיָה זֶה שֶׁמֵּינִיקָה כְּמוֹ מִין אַחֵר, וַאֲפִלּוּ כְּמִין חֲזִיר, פְּטוּרָה מֵהַבְּכוֹרָה.

If he bought a suckling animal from an idolater, he need not be concerned lest she is suckling the young of another; rather she stands under the presumption that she has borne. And even if the one she is suckling looks like another kind, and even like a kind of pig, she is exempt from the law of the firstborn.

Se’if 3ג׳

וְכֵן בְּהֵמָה שֶׁהִיא חוֹלֶבֶת, פְּטוּרָה מֵהַבְּכוֹרָה, שֶׁרֹב הַבְּהֵמוֹת אֵינָן חוֹלְבוֹת אֶלָּא אִם כֵּן יָלְדוּ. הַגָּה: וְיֵשׁ אוֹמְרִים דְּאֵין סוֹמְכִין עַל מַה שֶּׁהִיא חוֹלֶבֶת (טוּר בְּשֵׁם ה"ג וְהַגָּהוֹת מָרְדְּכַי פֶּרֶק הָאִשָּׁה), וְכֵן פָּסְקוּ הָאַחֲרוֹנִים (מהרא"י בִּפְסָקָיו סִימָן קס"ו ובת"ה סִימָן רע"א ומהרי"ו סִימָן קע"ד), וְכֵן נוֹהֲגִין בְּכָל מְדִינוֹת אֵלּוּ. מִיהוּ אִם יֵשׁ עוֹד צַד הֶתֵּר לָזֶה, אוֹ שֶׁעוֹבֵד כּוֹכָבִים מֵסִיחַ לְפִי תֻּמּוֹ שֶׁלֹּא לְהַשְׁבִּיחַ מִקְּחוֹ, וְאוֹמֵר שֶׁיָּלְדָה, סוֹמְכִין לְהַתִּיר. וְדַוְקָא בְּפָרוֹת, וּבְמָקוֹם שֶׁלֹּא נִשְׁמַע שֶׁחוֹלְבוֹת בְּלֹא וָלָד; אֲבָל בְּעִזִּים, שֶׁדֶּרֶךְ שֶׁחוֹלְבוֹת בְּלֹא וָלָד, לֹא סָמְכִינַן עַל כָּךְ אֲפִלּוּ בְּמָקוֹם דְּאִכָּא סְפֵק סְפֵקָא, כְּגוֹן שֶׁיָּלְדָה ב' וְאִכָּא לְמֵימַר אָכַל אֶחָד דְּאֵינוֹ בְּכוֹר, אֲפִלּוּ הָכִי אָסוּר (פִּסְקֵי מהרא"י סִימָן ק"ל). ונ"ל דִּבְמָקוֹם דְּאֵין דֶּרֶךְ הָעִזִּים בְּכָךְ, אוֹ שֶׁדֶּרֶךְ הַפָּרוֹת בְּכָךְ, אֵין לְחַלֵּק, וְיֵשׁ לַחֲקֹר אַחַר זֶה.

And likewise an animal that gives milk is exempt from the law of the firstborn, for most animals do not give milk unless they have borne. Hagah [Rema]: And some say that one does not rely on the fact that she gives milk (Tur in the name of the Behag, and Hagahot Mordechai, chapter "The woman"), and so the later authorities ruled (Maharai in his Pesakim, siman 166, and Terumat haDeshen, siman 271, and Maharyu, siman 174), and so is the practice in all these countries. However, if there is a further ground for permitting in this, or the idolater speaks in his innocence, not in order to raise the worth of his sale, and says that she has borne, one relies on it to permit. And this is specifically with cows, and in a place where it is not heard of that they give milk without an offspring; but with goats, whose way is to give milk without an offspring, we do not rely on this even where there is a double doubt — such as where she bore two, and one can say that he ate one that is not a firstborn — even so it is forbidden (Piskei Maharai, siman 130). And it seems to me that in a place where that is not the way of goats, or where that is the way of cows, one should not distinguish; and this needs to be investigated.