Esau was coming to see Jacob with an army of 400 people and the intention to kill him. Jacob sent messengers to Esau delivering the message (Genesis 32:6)
“וַיְהִי-לִי שׁוֹר וַחֲמוֹר, צֹאן וְעֶבֶד וְשִׁפְחָה; וָאֶשְׁלְחָה לְהַגִּיד לַאדֹנִי, לִמְצֹא-חֵן בְּעֵינֶיךָ”
“I have oxen and donkey and sheep and a slave and a female servant; and I have sent to tell my lord, that I may find favor in your sight.”
Jacob was very wise and the message was on different levels. Rashi, the great Torah commentator explains that the messengers were actual angels to tell us that the message was beyond the simple words. The angels prepared a track of light between Jacob and Esau. On the simple level, the message expressed humility and desire to please Esau. The Zohar explains that Jacob wanted to show Esau that he was working for Laban and didn’t enjoy the riches of the earth as his father blessed him with (Genesis 27:28) as firstborn.
I heard from Rabbi Ben Zion Mutzafi Shlita that on a deeper level the mention of Ox represents the power of Joseph that no evil eye could harm him. The donkey is the power of Issachar, who was very wise (Genesis 49:14), and dedicated all his time to the study of Torah. The flock represents the Israelites (Ezekiel 34:31), Jacob’s children that were all righteous and powerful.
Jacob avoided conflicts with his brother and did his best to please him. At the same time, he was ready to fight. The deeper level of the message is a testimony to Jacob’s trust and certainty with the gifts given to him by the Holy One Blessed be He, to help him at all situations.