Nonreturn rates of dairy cattle following uterine body or cornual insemination.

In the dairy cattle industry, uncertainty still remains regarding the most desirable site of inseminate deposition to maximize AI conception rates. The effect of site of inseminate deposition on nonreturn rates was determined from 2195 cornual and 2428 uterine body-bred dairy cattle. Twelve technicians from various areas of Pennsylvania and New York were chosen on the basis of their accuracy of semen deposition in retraining sessions, average nonreturn rates, and their willingness to cooperate in the study. For a 3-mo period (June, July, and August 1988), technicians alternated weeks of cornual and uterine breeding on all dairy cattle inseminated. One-half (.25 ml) of each semen unit was deposited approximately 5.1 cm into each uterine horn for cornual insemination. No significant difference in nonreturn rates was found between horn-bred (70.8%) and body-bred (69.5%) cows. The range of differences in percent nonreturn rates for technicians was 19 and 30% for body and cornual inseminations, respectively. A significant difference in nonreturn rates was found between technicians and between months with significantly higher average nonreturn rates (6.8%) in June. Cornual and uterine body deposition of semen yielded similar results; therefore, depositing an inseminate in the uterine horns to maximize fertility is unnecessary.