The biggest advantage of Veterinary Ultrasound tomography is its non-destructive nature. It can repeatedly explore the reproductive tract of female animals without damaging the reproductive performance of animals, and has become an excellent clinical diagnosis and research method in the field of cattle reproduction. Many foreign scholars have conducted a large number of studies on early pregnancy diagnosis in ruminants. Curran (1986) used a 5.0 MHz linear array probe to conduct a systematic study on first-time mating heifers and found that the embryo sac was scanned at 10-17 days and the fetus was scanned at 19-24 days. This research started relatively late in China and was limited to breeds such as dairy cows, goats, and sheep. Chen Zhaoying et al. (1996) observed the fetus at 19-20 days after sheep mating and observed the heartbeat at 20-22 days, which advanced the time for diagnosing sheep pregnancy by 3 to 5 days. However, there is no domestic data on this aspect of beef cattle. Therefore, this experiment uses the British BCF veterinary B-ultrasound Easi-scan portable veterinary B-ultrasound diagnostic instrument to make a preliminary attempt in the diagnosis of early pregnancy in beef cattle production. The purpose is to explore the appropriate application and significance of B-ultrasound in beef cattle production and provide valuable data for beef cattle breed improvement and production.

Materials and methods

1. Instruments and equipment

The British BCF veterinary B-ultrasound Easi-scan portable veterinary B-ultrasound diagnostic instrument (referred to as B-ultrasound), equipped with 5. OMI--Iz linear array rectal probe; disposable gloves, medical coupling agent (can be replaced by vegetable oil), digital camera, etc.

2. Test animals

The test animals are American shorthorn cattle and local yellow cattle 30 days after mating.

3. Examination method

Before the B-ultrasound pregnancy examination, first clear the feces in the rectum out of the rectum, and then, when performing the cow pregnancy examination, the linear array probe coated with coupling agent is sent to the position where the uterus can be touched in the rectum, and the sagittal and transverse scans are performed respectively to observe the changes in the image. During the exploration, the image of the uterine wall must be found first. After confirming that the uterus has been scanned, the exploration can continue within the scope of the uterine cavity. The probe should be moved slowly, and similar images should be scanned repeatedly until they can appear repeatedly and are fixed structures. The image is frozen and memorized. At the same time, the electronic ruler of B-ultrasound is used to measure and record the frozen image. Use a digital camera to take the screen section sound image and input it into the computer for image processing.

5. Judgment criteria

In the B-ultrasound image, the uterus of an empty cow is weakly reflected, and there is no obvious thickening change in the uterine wall. The main basis for the diagnosis of early pregnancy is the detection of embryonic sacs in the uterus, that is, the dark area in the uterus, embryonic spots, that is, the fetal body reflection (weakly reflected light spots in the dark area of the uterus), and embryonic heart beats, which are pulsating flashing light spots in the embryonic spots. At the same time, the detection of a small uterine dark area near the uterus and bladder is an important sign for the diagnosis of early pregnancy.

Veterinary B-ultrasound image of the uterus of a pregnant cow

The echo of the placental process can be seen when the cow is explored from another direction. The smooth interface between the uterus and the rectum has high brightness due to multiple reflections; the uterine wall below has a low attenuation of ultrasound by the fluid in the uterine cavity, and the echo of the uterine wall is enhanced. The allantois can be identified in the figure through a not very strong echo band. The cow is in the 28th to 31st day of the embryonic period of pregnancy. Since the cow embryo has developed to the tail bud embryo stage, it is C-shaped, and it is a C-shaped light spot in the sonogram.

Ultrasound image of the uterus of a cow with endometritis

The sonogram of endometritis in local yellow cattle. Due to inflammation in the uterus, the uterine wall thickens, the endometrium is shed in large quantities, and a large amount of tissue fragments and inflammatory exudate appear. Many light spots and dark areas can be observed in the sonogram.

Discussion and summary

Ultrasound image of the uterus of an empty-stomach cow

When the cow is pregnant, its uterine wall will thicken. Scanning image of an empty-stomach cow in the United States. The uterine wall of an empty-breasted cow is very thin, and it is difficult to see the complete uterine wall structure when using B-ultrasound rectal exploration. There are only some scattered echo bands, and the bladder is below the image. Common methods for diagnosing early pregnancy in animals include observing whether estrus occurs again after mating and traditional rectal examination, radioimmunoassay and enzyme-linked immunosorbent assay of progesterone, ultrasound diagnosis, and finding specific early pregnancy factors for monitoring. Observing estrus not only requires a lot of time and manpower, but also has an accuracy of only 70%, and ultrasound diagnosis records cannot meet the accuracy requirements of early diagnosis; traditional rectal examination can usually only be performed in about 40 days. Although its accuracy is high, the requirement for early pregnancy diagnosis is to ensure that the cow completes a reproductive cycle within 365 days. Such a detection method cannot guarantee the normal reproduction of cattle. The application of enzyme-linked immunosorbent assay (ELISA) technology and the use of monoclonal antibodies have improved the sensitivity of the determination, simplified the determination method, and shortened the time required for the determination. However, due to the high requirements for the experimental conditions required for the determination and the inconvenience of carrying the required instruments and equipment, it is not easy to promote it in clinical early pregnancy diagnosis. In contrast, B-ultrasound early pregnancy diagnosis is fast, simple, and highly accurate. It displays early pregnancy in real-time images, is intuitive, and has little stress on the uterus and fetus and is non-destructive.

This experiment used the British BCF veterinary B-ultrasound Easi-scan portable veterinary B-ultrasound diagnostic instrument to make a preliminary attempt to diagnose early pregnancy in beef cattle production. From the results obtained, B-ultrasound for pregnancy diagnosis in beef cattle has the characteristics of convenience, intuition, and high accuracy, and can be promoted and applied in beef cattle production. Although B-ultrasound pregnancy diagnosis, as an emerging technology, has advantages that traditional methods cannot match, and the reported accuracy is very high, it is currently only in the field of scientific research and teaching in China, and has not been promoted and applied in production. In this experiment,

the reasons why ultrasound early pregnancy diagnosis has not been widely used were analyzed: first, the price of ultrasound diagnostic instruments is expensive; second, B-ultrasound early pregnancy diagnosis requires high rectal exploration skills of the operator. Only in this case can the operator be guaranteed to use the B-ultrasound probe to find the corresponding uterine part in the rectum. At the same time, animal obstetric diseases have a certain impact on the positive coincidence rate of ultrasonic pregnancy diagnosis in maternal livestock, such as embryonic death, embryo resorption and abortion, uterine adenoma, uterine pyometra, uterine hydrops, etc., and these related issues still need further research.