Effect of Clitoral Stimulation and Length of Time to Complete AI on Pregnancy Rates in Beef Cattle

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Abstract
An experiment was conducted to determine the effects that various durations of clitoral stimulation (CS) and length of time to complete inseminations (T-AI) have on first service AI pregnancy rates (PR). The experiment was conducted over 3 consecutive years on a total of 1,544 yearling heifers and lactating cows (2 to 11 years old). Cattle were randomly assigned within age, breed and sire to receive either 0, 3 or 10 sec of CS post-AI. In cows, CS increased PR but 3-sec CS was not significantly greater than 10 sec (51.7, 59.2 and 58.2% for 0, 3 and 10 sec). In heifers, the effect of CS on PR was nonsignificant and there was no effect of 3 sec vs 10 sec (57.5, 53.9 and 54.2% for 0, 3 and 10 sec). T-AI averaged 1.33 min, was longer in cows than heifers, was shorter in inseminations resulting in a pregnancy than those that did not and tended to decrease PR when times exceeded 4 minutes. Conclusions are that: (1) CS increased PR in lactating cows but not heifers; (2) the effects of CS in cows were modified by T-AI; (3) failure to obtain a response to CS in heifers was not explained by differences in T-AI; (4) T-AI should be 2 min or less, although an acceptable PR is possible at longer times if semen placement is at least at the second cervical ring. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.