Can babies below 12 months old have cows milk mixed in breast milk?

Hi mommas

I was wondering if 10 month old babies can have whole milk?

My baby is breastfed but im a exclusively pumping mom and it seems that im not producing enough but is just 1oz short per bottle feeding. I want to keep giving my baby breastmilk so i was wondering if i can mix in whole milk in the breastmilk to make up for the amount im short at.

Thank you!