ensure your bottle and pump parts are clean and sterlized before use.breastmilk stays fine in room temperrature for 6 hours and in refrigerator for 24 hours.You can keep in fridge,before giving to baby keep bottle in a bo0wl of warm water so that milk comes to room temp.DO not boil/microwave breastmilk

The best way is direct breast feeding which besides having multiple nutritional and immunological benefits, increases the bond between baby and mother. But in case you need to store breast milk for some reasons, collect the milk in a clean Steel Katori rather than plastic bottle. this can be given immediately , stored at room temperature of 24-28 degrees celsius upto 4 hours and in refrigerator upto 8 hours. You can feed your baby with katori chamach which is anyday superior to bottle feeding. With bottle, hygiene is tough to maintain and baby may develop infections.