**1. Introduction**

The ultrasound technology has been used for various functions particularly as a tool in beef and dairy research for many years. It has become more available to the commercial livestock agriculture recently. Application of transrectal real-time ultrasonography in the study of bo‐ vine reproduction represents a technological breakthrough that has revolutionized the knowledge of reproductive biology [Boyd and Omran, 1991]. New research results derived from ultrasonic imaging has clarified the complex nature of reproductive processes such as ovarian follicular dynamics, corpus luteum function, and foetal development in farm ani‐ mals. Extensive adoption and use of ultrasonography for routine reproductive examinations of dairy cattle is its highest contribution to the dairy industry.

Practical applications of ultrasound in bovine reproduction include imaging of the ovary as a diagnostic aid, examination and confirmation of ovarian cysts, early pregnancy detection, identification of twins and foetal sexing [Fortune et al, 1988; Garcia et al, 1999; Noble et al, 2000 Lamb, 2001; Stroud, 2006]. Although rectal palpation is the established method for con‐ ducting reproductive examinations, the information-gathering capabilities of ultrasonic imaging far exceed those of rectal palpation. Assessment of pregnancy status and foetal via‐ bility early post breeding can significantly improve reproductive efficiency. Such methods can play a key role in reproductive management to rapidly return open animals to the breeding program. Early pregnancy detection is only useful when techniques have a high level of accuracy for detection of both pregnant and non-pregnant animals.

Early ultrasonic identification of twinning or male calves in dairy cows allows for imple‐ mentation of differential management strategies such as termination of the unwanted preg‐ nancy or to mitigate the negative effects of twinning during the periparturient period. Ultrasound can accurately determine the presence of a viable embryo as early as 21 days af‐

© 2013 Lemma; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ter AI. The accuracy of detecting foetal viability may approach 100% [Lamb, 2001]. A techni‐ cian with a trained eye has the capability of accurately assessing the age of the foetus based on foetal size [Curran, 1986]. At 60 to 85 days of pregnancy the trained user can even deter‐ mine foetal sex by the absence and/or presence of the foetal genitalia with over 95% accura‐ cy. These two features alone provide many options for the use of ultrasound in reproductive management practices [Palmer and Drinacourt, 1980; Muller and Wittkowski, 1986; Kastelic et al, 1989; Romano and Masgee, 2001]. Development of integrated reproductive manage‐ ment systems that combines ultrasound with new and existing reproductive technologies will further enhance the practical applications of ultrasonography. In summary, current and future applications of ultrasonography hold tremendous potential to enhance reproductive management and improve reproductive efficiency in bovine.

The incorporation of ultrasound in reproductive research has also led to greater understand‐ ing of ovarian physiology. Ultrasound has been used extensively in the development of con‐ trolled breeding programs involving both oestrus and ovulation synchronization for effective timed AI. Sequential monitoring of dynamic changes in a follicular population dur‐ ing the oestrous cycle has been made possible by ultrasonography [Driancort et al, 1991; Garcia et al, 1999; Ginther 1993]. This capability has helped unlock some of the mysteries of folliculogenesis. During anoestrous, inactive ovaries are readily differentiated from func‐ tional ovaries with ultrasonography.

**Figure 1.** Several medium sized follicles observed in mare. Ultrasonogram taken with 5MHz curvilinear array scanner

The Role of Trans-Rectal Ultrasonography in Artificial Insemination Program

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Follicles as small as 2 - 3 mm can be seen and the corpus luteum can usually be identified throughout its functional life [Lemma et al, 2006] Estimating the stage of oestrous cycle, as‐ sessing the status and number of preovulatory follicles, determining ovulation, monitoring the development and morphology of corpus luteum are among the potential applications of ultrasonographic examination of the ovaries [Fortune et al, 1988; Garcia et al, 1999; Noble et al, 2000; Evans et al, 2000; Evans, 2003]. The number and sizes of follicles on a given ovary will vary widely and are dependent on the time of year and the reproductive stage in differ‐ ent animals [Vandeplassche et al, 1981; Perry, 1991; Godoi et al, 2002]. Many small follicles are observed during early dieostrus and these follicles will grow larger at mid-cycle. The dominant or ovulatory follicle will develop at a rate of 1.5 to 2.5mm per day in cattle [Drian‐ court et al, 1988] few days before ovulation which are all easily monitored ultrasonically to determine the date of ovulation and hence subsequently fix the appropriate time for insemi‐ nation. During oestrous cycles in cattle dominant follicles reach a maximum diameter of ap‐ proximately 10 - 20 mm and the largest subordinate follicles reach maximum diameter of approximately 8 mm. Cows ovulate at about 12 hours after the end of the oestrus period. The time for insemination may therefore range between 6 and 24 hours prior to ovulation

The appearance of dominant follicles is often accompanied by an outward manifestation of behavioural oestrus. However, cows with dominant follicle that is about to ovulate do not always show overt oestrus and this is becoming one of the greatest hindrance to the success of AI. Whilst good oestrus detection does not necessarily guarantee good reproductive per‐ formance, poor oestrus detection makes poor performance hard to avoid [Arthur, 2001]. Poor oestrus manifestation and failure to detect oestrus further hinders insemination at the correct time which is an important cause of fertilization failure. Insemination very early in

(Hitachi 405, Germany). Source: Lemma et al, 2006

[Arthur, 2001; Ball and Peters, 2004]

Further, when choosing bulls, many producers are faced with difficult decisions regarding the contributions of both maternal and carcass traits. Not only do the attributes of multiple breeds vary, but variation within breed is also substantial. By combining ultrasound and AI, a producer can develop a breeding program that optimizes both maternal and carcass traits [Travene et al, 1985; Kahn, 1992]. Using ultrasound, producers may determine females that are pregnant with AI-sired heifer calves based on the age and sex of the foetus [Travene et al, 1985; Kahn, 1992]. In a typical commercial cow-calf production environment controlled breeding seasons range from 60 to 120 days. By using ultrasound as early as 30 days after the end of the breeding season in seasonally breeding animals, producers can divide their herd into cows that became pregnant early or late in the breeding season, and open cows which can subsequently be managed appropriately in accordance with their reproductive status to run the production at reasonable cost.
