וַיִּתֵּן֙ בְּיַד־עֲבָדָ֔יו עֵ֥דֶר עֵ֖דֶר לְבַדּ֑וֹ וַ֤יֹּאמֶר אֶל־עֲבָדָיו֙ עִבְר֣וּ לְפָנַ֔י וְרֶ֣וַח תָּשִׂ֔ימוּ בֵּ֥ין עֵ֖דֶר וּבֵ֥ין עֵֽדֶר׃
And he placed them in the hand of his servants, drove by drove alone; and he said to his servants: Pass on before me, and put a space between drove and drove.
Rashi on Bereishis 32:17, citing Bereshit Rabbah 76:8 for the spacing between the droves.
Sefaria · Rashi on Genesis 32:17
עֵדֶר עֵדֶר לְבַדּוֹ — כָּל מִין וּמִין לְעַצְמוֹ. עִבְרוּ לְפָנַי — דֶּרֶךְ יוֹם אוֹ פָּחוֹת וַאֲנִי אָבֹא אַחֲרֵיכֶם. וְרוֶחַ תָּשִׂימוּ — עֵדֶר לִפְנֵי חֲבֵרוֹ מְלֹא עַיִן, כְּדֵי לְהַשְׂבִּיעַ עֵינוֹ שֶׁל אוֹתוֹ רָשָׁע וּלְתַוֵּהוּ עַל רִבּוּי הַדּוֹרוֹן.
Rashi explains that each species was kept in its own drove; the servants were to go ahead, while the droves were spaced far enough apart to fill Esau's eye and impress him with the abundance of the gift.
The spacing was part of Yaakov's strategy for presenting the gift in successive stages rather than as one undifferentiated mass.
Commentary on the structure and presentation of Yaakov's gift.
Rashi connects the physical spacing of the droves with Yaakov's effort to make the size of the gift conspicuous to Esau.