ग्राम्यपशुसंघेष्वतरुणेषु स्त्री

The feminine noun is only retained when denoting a collection of domestic animals, not being young.
As a general rule, when there is a compounding of masculine and feminine nouns, the masculine noun is retained (see 1.2.67). The present sutra is an exception to that rule. It ordains that when there is a compounding of words denoting group of domestic animals, of different genders, the feminine noun is preferred; provided that the words should not relate to the young of such animals. The word 'ataruna' in the aphorism qualifies the word 'pasu' with which it is in construction, and not the word 'sangha.' As गाव इमाः 'these cows (and bulls);' अजा इमाः 'these goats' (both males and females).

The rule only applies to domestic (gramya) animals and not to wild animals; and only to beasts (pasu) and not men. As रुरव इमे, 'these wild deers' (male and female); पृषता इमे, 'these antelopes' (male and female); ब्राह्मणाः, 'the Brahmanas (male and female); क्षत्रियाः, 'the Kshatriyas.' In all these the masculine noun is retained by Rule 1.2.67.

Vart:- This rule must be confined to domestic animals having divided hoof. Therefore अश्वा इमे, 'these horses' (male and female). Here the masculine noun is retained, because horse has no divided hoof.

Why have we used the word (sangha) "collection"? Observe एतौ गावौ चरतः, 'these two cows are grazing.' Here the word 'gavau' does not connote 'bull' also.

Why do we say "not being young?" वत्सा इमे 'these calves'; बर्करा इमे 'these kids.' Here the masculine noun is retained by the application of Rule 1.2.67.