If your diet is correct, cardio is not necessary during a bulking cycle. Yes, it can hinder your gains. I think a lot of consideration should be given to your metabolism, your goal and your level of cardio before starting the program. If you have been doing a lot of cardio over a long period of time, it will not have as much of an impact than if you haven't and you want to sart now. For myself as an example, I only do cardio when absolutely necessary. I have also found it beneficial to seperate the cardio workout from your weight training.