Breast milk to cows milk

Tatiana🇨🇷♈️💍🇩🇴♏️ • Happily Married. 💏 👰🏽 12.19.08 💙 07.10.16 💓 02.29.20 💙 🐸 🤱🏽BreastMILK is best 🚫 formula

Our leap year 🐸 baby I guess technically won’t be 1 until 3/1?? 🤣 do you guys think it’s too early to start mixing cows milk with his breast milk ?? He drinks 0 formula and once he turns 1 I can no longer legally pump at work. Suggestions??! Thanks in advance 🤗