when to fatten a bull

[scf84]

i would like to finish a bull out to butcher, all i have now is a 425lbs 5 1/2 month old brangus mix.
how old and big do i need to let hem get before i lock him in a pen to fatten.

 

[Son of Butch]

750 lbs or 1 year whichever comes first, but why don't you castrate him?