**3. Application of ultrasonography in early PD**

Reproductive ultrasonography has increased the knowledge of the changes during early pregnancy in different animals. With the use of a real-time, B-mode ultrasonography and 5 MHz transducer, pregnancy can be detected as early as 9 to 12 days post AI into gestation [Pierson and Ginther, 1984; Curran et al., 1986; Boyd et al., 1988]. A thorough understanding of the ultrasonic anatomy and dynamic changes in the uterus is essential for accurate preg‐ nancy detection. The embryo initially appears as a short line (Day 20-22), later becomes Cshaped (Day 22-30), and finally, by Day 30-32 of gestation assumes an L- shape (Fig 2). Although the embryo can first be detected between Days 19 and 24 of gestation [Curran et al., 1986], it is most practical to scan females which are expected to have embryos that are >26 days of age. The bovine foetus can be visualized beginning at day 20 post breeding and continuing throughout gestation, however, because of its size in relation to the image field of view, the foetus cannot be fully imaged after 90 days using high frequency transducers.

Ultrasound is a rapid method for pregnancy diagnosis, and experienced palpators adapt to ultrasound quickly. This is particularly important to lessen the effect of early scanning on embryonic survival. The time required to assess pregnancy in beef heifers at the end of a 108-day breeding season averaged 11.3 seconds using palpation per rectum versus 16.1 sec‐ onds required to assess pregnancy and foetal age using ultrasound (Galland et al., 1994). Two points must be considered when using ultrasound for routine early pregnancy diagno‐ sis in a cow herd. First, when using ultrasound for early pregnancy diagnosis, emphasis must be given to identifying non-pregnant rather than pregnant cows. Second, a manage‐ ment strategy must be implemented to return the non-pregnant cows to service as quickly as possible after pregnancy diagnosis. Such strategies include administration of PGF2α to cows with a responsive CL, use of estrus detection aids, or a combination of both methods.

The Role of Trans-Rectal Ultrasonography in Artificial Insemination Program

http://dx.doi.org/10.5772/52721

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The main advantages of the use of ultrasound for pregnancy diagnosis are the high accuracy of the results and the relatively early confirmation of pregnancy. Mistakes can be made, no matter proficient the operator might be. Therefore, it is suggested that a female not be consid‐ ered non-pregnant until two negative scans have been obtained at a gestation age of at least 16 days. The main disadvantages of the use of ultrasonography are related to the cost and time involved. Ultrasound machines are relatively expensive. Pregnancy diagnosis with an ultra‐ sound machine takes more time than rectal palpation. Also the training required for proper in‐ terpretation of the images is another disadvantage. Cows diagnosed pregnant at an early ultrasound exam have a greater risk of early embryonic loss and, therefore, must undergo subsequent pregnancy examinations to identify and rebreed cows that experience such loss. If left unidentified, cows experiencing embryonic loss after an early pregnancy diagnosis would actually reduce reproductive efficiency by extending their calving interval (Fricke, 2002).

Prior to the development of ultrasound for pregnancy diagnosis in cattle, veterinarians were unable to accurately determine the viability or number of embryos or foetuses. Because the heartbeat of a foetus can be detected at approximately 22 days of age, one can accurately as‐ sess whether or not the pregnancy is viable. Studies in beef [Beal et al., 1992; Lamb et al., 1997] and dairy cattle [Smith and Stevenson, 1995; Vasconcelos et al., 1997; Szenci et al., 1998] have used ultrasound to assess the incidence of embryonic loss. The fertilization rate after AI in beef cows is about 90%, whereas embryonic survival rate is 93% by day 8 and only 56% by day 12 post AI [Diskin, and Sreenan, 1980]. The incidence of embryonic loss in beef cattle appears to be significantly less than in dairy cattle. Some reports [Beal et al., 1989; 1992; Lamb and Fricke, 2005] indicate a 6.5% incidence of embryonic loss in beef cows from day 25 to day 45 of gestation. In dairy cattle, pregnancy loss from 28 to 56 days after artifi‐ cial insemination may reach 13.5%, or 0.5% per day. Ultrasonography hence becomes a use‐ ful tool in the study of early embryonic death (EED), and to monitor the success of a

breeding program, by determining pregnancy rates and embryonic death.

Such strategies will significantly improve outcomes of AI in large herds.

**4. Early embryonic death (EED)**

**Figure 2.** Bovine embryo scanned on Day 26 of pregnancy using B-mode real time ultrasound with 5MHz linear array transducer

Accuracy of diagnoses improves, however, by Day 18 (85%), Day 20 (100%) and Day 22 (100%) of pregnancy (Kastelic et al., 1989). Presence and vitality of the embryo can be con‐ firmed by the detection of a heartbeat as early as 19 to 24 days of gestation. Early pregnancy detection has a greater economic significance particularly for the dairy industry. When an accuracy of over 99% is achieved, it enables to rapidly identify fertility problems. The rate of detection of early embryonic loss is thus also higher with 10 to 16% of cows diagnosed preg‐ nant at 28 days post AI experience early embryonic loss by 56 days post AI. Cows diagnosed pregnant at 28 days post AI using ultrasound should, therefore, be scheduled for a subse‐ quent examination around 60 days post AI, when the rate of embryonic loss per day de‐ creases dramatically.

In situations where the exact dates of AI are known, ultrasonography is simply used as a confirmation of pregnancy or to validate that detection of a viable embryo within the first two weeks of pregnancy. In contrast, another study showed diagnosis of pregnancy in hei‐ fers on day 10 through day 16 of gestation resulted in a positive diagnosis for pregnant or non-pregnant cows in less than 50%. On from days 18 - 22 of gestation, accuracy of pregnan‐ cy diagnosis improved from 85% to 100% [Lamb and Fricke, 2005]. Although an embryonic vesicle is detectable by ultrasound as early as 9 days of gestation, accuracy of detection ap‐ proaches 100% usually after day 25 of gestation. For practical purposes, the efficiency (speed and accuracy) of a correct diagnosis of pregnancy should be performed in cows expected to have embryos that are at least 26 days of age.

Ultrasound is a rapid method for pregnancy diagnosis, and experienced palpators adapt to ultrasound quickly. This is particularly important to lessen the effect of early scanning on embryonic survival. The time required to assess pregnancy in beef heifers at the end of a 108-day breeding season averaged 11.3 seconds using palpation per rectum versus 16.1 sec‐ onds required to assess pregnancy and foetal age using ultrasound (Galland et al., 1994). Two points must be considered when using ultrasound for routine early pregnancy diagno‐ sis in a cow herd. First, when using ultrasound for early pregnancy diagnosis, emphasis must be given to identifying non-pregnant rather than pregnant cows. Second, a manage‐ ment strategy must be implemented to return the non-pregnant cows to service as quickly as possible after pregnancy diagnosis. Such strategies include administration of PGF2α to cows with a responsive CL, use of estrus detection aids, or a combination of both methods. Such strategies will significantly improve outcomes of AI in large herds.

The main advantages of the use of ultrasound for pregnancy diagnosis are the high accuracy of the results and the relatively early confirmation of pregnancy. Mistakes can be made, no matter proficient the operator might be. Therefore, it is suggested that a female not be consid‐ ered non-pregnant until two negative scans have been obtained at a gestation age of at least 16 days. The main disadvantages of the use of ultrasonography are related to the cost and time involved. Ultrasound machines are relatively expensive. Pregnancy diagnosis with an ultra‐ sound machine takes more time than rectal palpation. Also the training required for proper in‐ terpretation of the images is another disadvantage. Cows diagnosed pregnant at an early ultrasound exam have a greater risk of early embryonic loss and, therefore, must undergo subsequent pregnancy examinations to identify and rebreed cows that experience such loss. If left unidentified, cows experiencing embryonic loss after an early pregnancy diagnosis would actually reduce reproductive efficiency by extending their calving interval (Fricke, 2002).
