According to smrti regulation, the cow is the mother and the bull the father of the human being.
Srimad Bhagavatam Canto Three Chapter Two Verse Twenty Nine S.B. 3/2/29
sa eva go-dhanam laksmya
carayann anugan gopan
sah--He (Lord Krsna); eva--certainly; go-dhanam--the treasure of cows; laksmyah--by opulence; niketam--reservoir; sita-go-vrsam--beautiful cows and bulls; carayan--herding; anugan--the followers; gopan--cowherd boys; ranat--blowing; venu h--flute; ariramat--enlivened.
While herding the very beautiful bulls, the Lord, who was the reservoir of all opulence and fortune, used to blow His flute, and thus He enlivened His faithful followers, the cowherd boys.