My daughter is already one ( a few weeks ago) and I stil bottle feed her with formula (Karicare Gold -Toddler) and I used warm cow's milk (Pura Milk Gold -Extra Creamy) to mix with her formula for one feed and use warm water to mix her formula for the next feed (Warm cow's milk or water mix more well)
My sister's feed their bubs cows milk at 1 yrs old and its ok for them to drink it cold (just advisable to heat it up when the weather is cold to keep their stomachs warm)
Its all a matter of choice. When bubz turn one they are strong enough to drink cow's milk because their immune system is well developed and stronger. At this age, they will be eating more and will get their nutrients from the food they are eating.
Personally I still want to feed my daughter the gold brand of formula (not essential) but it does have lot more nutrients then cows milk. I do try to feed her with the best food possible to help encourage her growth to be as healthy and productive as possible so she can reach her full potential.
I feed her cheese, yoghurt, veges and all the healthy foods her growing body needs (shes a very active girl)
Its all a personal choice, if you are keen to get ur boy to stop using the bottle, there are bottles design for different stages leading up to taking away the usage of a bottle and using a cup or sipper instead.
Hope this help.