When to Identify Nonpregnant Lactating Dairy Cows using Trasrectal Ultrasonography

Early identification of nonpregnant dairy cows post breeding can improve reproductive efficiency and pregnancy rate by decreasing the interval between AI services and increasing AI service rate. Thus, new technologies to identify nonpregnant dairy cows early after artificial insemination (AI) may play a key role in systematic management strategies to improve reproductive efficiency and profitability on commercial dairy farms. Transrectal palpation is the oldest and most widely used method for early nonpregnancy diagnosis in dairy cattle (Cowie, 1948); however, a newer technology may someday replace transrectal palpation as the method of choice for nonpregnancy diagnosis in the dairy industry. Two events must transpire before this transition occurs. First, a technology must be developed that exceeds transrectal palpation in one or more of the attributes of the ideal early nonpregnancy test. Second and no less important, this new technology must be practically integrated into a systematic on-farm reproductive management strategy and empirically demonstrated to exceed the status quo of the industry in reproductive performance. Results from several recent studies indicate that positive pregnancy outcomes diagnosed by transrectal ultrasonography conducted 26 or 27 d after timed AI may be inflated due to pregnancy loss and/or diagnostic errors compared to pregnancy outcomes conducted 32 to 39 d after timed AI. Furthermore, fertility to timed AI after resychronization of ovulation was greater when initiated 33 d after timed AI compared to 19 or 26 d after timed AI. Taken together, these results support the counterintuitive notion that delaying pregnancy diagnosis may improve reproductive efficiency when combining ultrasonography with a hormonal protocol for timed AI to program nonpregnant cows for rebreeding due to the high rate of pregnancy loss and errors occurring too early post TAI.