Recumbent of bulls (A) and arc back in bulls (B) during semen collection by different electro-ejaculation methods. Method I, EE device was switched on and continued until ejaculation; 1st stage of Method II, EE was switched on, increasing the electrical stimulus from zero until four cycles (1st stage took 16 s); 2nd stage of Method II, immediately after 1st stage, EE was switched on for the start of the 2nd stage. The process was repeated in the 2nd stage until the electrical stimuli was at eight cycles (2nd stage took 32 s); 3rd stage of Method II, EE was then switched off and switched on again to start the final 3rd stage, it was started from zero and continued until semen was emitted; ab values with different superscripts are significantly different among methods; n = 24.