The Gayatri is the first of all metres, goat is the first of all (sacrificial) animals, Kin are the first of all quadrupeds. The twice-born ones are the first of all human beings.
गायत्री च्छन्दसामादिः प्रजानां सर्ग उच्यते। गावश्चतुष्पदामादिर्मनुष्याणां द्विजातयः॥