Brihat Samhita
षष्भिर्दन्तैः सितऽभैर्भवति हयशिशुस्तैः कशायैर्द्विवर्षैः सन्दंशैर्मध्यमान्त्यैः पति समुदितैस्त्र्यब्धि पञ्चाब्दिकाश्वः । सन्दंशानुक्रमेण त्रिकपरिगणिताः कालिका पीतशुक्लाः काचा मक्षीक शङ्खावटचलनं अतो दन्तपातं च विद्धि ॥ ६६-०५ ॥
A colt has six white teeth. If the teeth be of brown colour, the animal is 2 years old; if the central and corner teeth in both lines have fallen and sprouted again, the animal is from 3 to 5 years old, according as the number of such teeth is 3, 4 or 5; if the lines known as Kālikā, Pīta (a yellow line), Śukta (black line), Kācā (white line), Makṣīka (of the colour of the bee) or Śaṅkha (of the colour of the conch shell) appear in the teeth, the age of the animal will respectively be from 6 to 8, 9 to 11, 12 to 14, 15 to 17, 18 to 20 or 21 to 23. If depressions appear in the teeth or if the teeth have begun to shake, or if they have fallen, the age varies from 24 to 60.
english translation
SaSbhirdantaiH sita'bhairbhavati hayazizustaiH kazAyairdvivarSaiH sandaMzairmadhyamAntyaiH pati samuditaistryabdhi paJcAbdikAzvaH । sandaMzAnukrameNa trikaparigaNitAH kAlikA pItazuklAH kAcA makSIka zaGkhAvaTacalanaM ato dantapAtaM ca viddhi ॥ 66-05 ॥
hk transliteration by Sanscript