Dear Sri Moorthy,
Everything in RV is so shrouded in mystery that a straight answer to your question is not possible. If the later Vedic literature conjectures Sarama to be a dog, Max Muller’s interpretation of Sarama to be the dawn is also a conjecture. Here is another conjecture of Aurobindo from his book ‘The secret of the vedas’.
I shall suggest that Dakshina like the more famous Ila, Saraswati and Sarama, is one of four goddesses representing the four faculties of the Ritam or Truth- consciousness,— Ila representing truth-vision or revelation, Saraswati truth-audition, inspiration, the divine word, Sarama intuition, Dakshina the separative intuitional discrimination. Daksha then will mean this discrimination whether as mental judgment on the mind-plane or as intuitional discernment on the plane of the Ritam.
You can make your own conjecture after reading the following translation of the verses (wherever the word Sarama occurs) by Griffith, which is almost the same as that of Sayana. Wherever they differ, the translation of Griffith is given in red and that of Sayana in blue.
It seems to me that some light will be thrown in the otherwise total darkness once we fix the exact meaning of rtam.
1.62.3 When Indra and the Angirases desired it, Sarama found provision for her offspring.
Brhaspati cleft the mountain, found the cattle: the heroes shouted with the kine in triumph.
1.72.8 Knowing the rtam (law) (sacrifice), the seven strong floods from heaven, full of good thought, discerned the doors of riches.Sarama found the cattle's firm-built prison whereby the race of man is still supported.
3.31.6 When Sarama had found the mountain's fissure, that vast and ancient place she plundered thoroughly./ Indra made ample provision for her young. In the floods' van she led them forth, light-footed: she who well knew came first unto their lowing.
4.16.8 When, Much-invoked! the water's rock / cloud for the escape of waters thou cleftest, Sarama showed herself and went before thee. Hymned by Angirases, bursting the cowstalls, much strength thou foundest for us as our leader.
5.45.7 Here, urged by hands, loudly hath rung the press-stone wherewith Navagvas through ten months sang praises. Sarama went aright and/ going to the ceremony found the cattle. Angiras gave effect to all their labours.
5.45.8 When at the dawning of this mighty Goddess, Angirases all sang forth with the cattle,-
Their spring was/ milk was offered in the loftiest place of meeting,-Sarama found the kine by rtam's Order's /truth’s pathway.
RV tenth mandala (considered to be a later day addition)contains a dialogue between panis and Sarama. It is reproduced here.
10.108.1. WHAT wish of Sarama hath brought her hither? The path leads far away to distant places.
What charge hast thou for us? Where turns thy journey? How hast thou made thy way o'er Rasa's waters.
2 I come appointed messenger of Indra, seeking your ample stores of wealth, O Panis.
This hath preserved me from the fear of crossing: thus have I made my way o'er Rasa's waters.
3 What is that Indra like, what is his aspect whose envoy, Sarama, from afar thou comest?
Let him approach, and we will show him friendship: he shall be made the herdsman of our cattle.
4 I know him safe from harm: but he can punish who sent me hither from afar as envoy.
Him rivers flowing with deep waters bide not. Low will ye be, O Panis, slain by Indra.
5 These are the kine which, Sarama, thou seekest, flying, O Blest One, to the ends of heaven.
Who will loose these for thee without a battle? Yea, and sharp-pointed are our warlike weapons.
6 Even if your wicked bodies, O ye Panis, were arrow-proof, your words are weak for wounding;
And were the path to you as yet unmastered, Brhaspati in neither case will spare you.
7 Paved with the rock is this our treasure-chamber; filled full of precious things, of kine, and horses.
These Panis who are watchful keepers guard it. In vain hast thou approached this lonely station.
8 Rsis will come inspirited with Soma, Angirases unwearied, and Navagvas.
This stall of cattle will they part among them: then will the Panis wish these words unspoken.
9 Even thus, O Sarama, hast thou come hither, forced by celestial might to make the journey.
Turn thee not back, for thou shalt be our sister: O Blest One, we will give thee of the cattle.
10 Brotherhood, sisterhood, I know not either: the dread Angirases and Indra know them.
They seemed to long for kine when I departed. Hence, into distance, be ye gone, O Panis.
11 Hence, far away, ye Panis! Let the cattle lowing come forth as holy Law commandeth,
Kine which Brhaspati, and Soma, Rsis, sages, and pressing-stones have found when hidden.