Below are links to a couple of papers on simialr subjets. Based on the data from these papers; and, the experiances mentioned on this board it would seem that the answer to whether it is more cost effective to casterate or not is............... drum roll please................It all depends. Surprise, surprise.
Where the main dependcies are:
1) Age at which the calves are sold since ADG and total weight is a funtion of age and is different for steer vs. bull.
2) Local market delta/dock for steer vs. bull.
3) Calf management techniques employed, (i.e. age and cost of castration, associated probability of increased medical costs, elapsed time after casteration to sell, type of feed, placement of bulls near cows which preoccupy the bulls from grazing, etc...
As is often the case, the answer to whether or not something is cost effective depends alot on how well the the specifics of the supply side operation match the local demand environment. IMHO.
Here's the links
http://ohioline.osu.edu/sc181/sc181_16c.html
http://www.ansi.okstate.edu/research/2003rr/14/14.htm