You can dehorn later, but you need the right equipment....
Firstly, if the horns are well grown you need to cheese wire them off. You need to have someone experienced at this, as its important to get a good momentum going, keeping friction producing heat, which helps to quaterise as you go.
A de horning iron should then be used immediatley after the horn is removed to finish the quaterising, and not stopped till no more blood ouzes/spurts.
You then need to be vidgellent to keep flies off etc, and check for secondary infections..... purple spray works well.
I'm not sure about where you are