Why does the Torah add the word "Echad" regarding each of the species?
Rashi (citing the Sifri): To teach us that it was a prize animal (Meyuchad she'be'Edro). 1
Moshav Zekeinim (in Pasuk 21): zThe Gemara states in Shavu'os 15a, it that [size] is not important to Hashem? (He seems to be querying Rashi, but Rashi did not say that it is superior due to its size! - PF)
What is the significance of the three animals ? the bull, the ram and the lamb that the Nesi?im brought as an Olah?
Rashi (in Pasuk 21, citing R. Moshe ha'Darshen): They correspond to Avraham, Yitzchak and Ya'akov, 1 respectively (representing Z'chus Avos. 2
Rashi: See Bereishis 18:7, 22:13, 30:40, respectively. Ba'al ha'Turim: The Gematriyah of 'Par, Ayil Keves' is equivalent to that of 'Avraham, Yitzchak and Ya'akov'.
Ramban (in Pasuk 2, citing Bamidbar Rabah) and Hadar Zekeinim (in Pasuk19): And the Torah was given in the merit of the Avos.