BREED DIFFERENCES IN THE RESPONSE OF YOUNG BEEF BULLS TO ELECTRO-EJACULATION

SUMMARY A total of 702 electro-ejaculation attempts are recorded on young (16 to 31 months) beef bulls of 3 breeds and 3 breed crosses (Brahman cross 100, Africander cross 93, Shorthorn cross 109, Brahman 81, Africander 89, and Hereford 230. Four hundred and forty of these attempts were conducted on bulls of the first 5 of these breeds which had been reared under similar conditions on the same property. The machine employed was a Watson Transtimulator, powered by a 12-volt automobile battery, and connected to a 6.25 cm diameter bipolar ring electrode probe, 37.5 cm in length. The voltages at which the sperm free (sample A) and sperm rich (sample B) samples were initiated were 4.8 ± .2 and 7.7 ± .2 volts respectively. No breed differences occurred. Breed differences occurred in the proportion of bulls showing a severe reaction to the electricity (P < 0.001) with the Africander (32.6% P < 0.001) and Ax (28.0% P < 0.01) having the highest proportions of severe reactions. These 2 breed groups also had the highest proportions of electro-ejaculation failures (respectively, 23.6% P < 0.05 and 19.4% n.s.). Overall, bulls of Bos indicus derivation did not differ from those of Bos taurus derivation in electro-ejaculation failures. During stimulation, erection was achieved by 19.8% of bulls and failure to collect an assessable ejaculate occurred in 15%. No breed differences occurred in either category. Collapse during stimulation occurred in 5.3% of electro-ejaculation attempts (overall P < 0.05) with the SH breed group having highest representation (12.8% P < 0.001).