I don't know if you "can" but I don't think you "should", and I don't think it's recommended. Each day your milk will taste different - due to the different things you eat yourself. So it's not recommended that you mix milk that is not within 24 hours of eachother because it might taste odd to your little one, and they may not eat it. However, you can feed BOTH to your little one - no problem!
Just use two bottles and if he/she won't eat them back to back, just try waiting 30+ minutes and trying it again.
