When the cow is 26-30 days pregnant, the fetus is observed by B-ultrasound. The fetus is 0.96cm long, the cow's uterine horn is dilated, with a liquid dark area inside, the diameter of the uterine horn cavity is 4.17*2.45cm, the thickness of the uterine horn wall is 0.55cm, the near field of the cow B-ultrasound is a gray echo area, and the far field of the cow B-ultrasound is a strong echo area; the amniotic sac is visible, and the amniotic membrane is a strong echo halo with a diameter of 1.75*1.17cm: the fetus is strongly echoed, basically close to the amniotic sac, and there is a narrow and quiet gray echo area between the two.

When the cow is 36-40 days pregnant, the fetus is observed by B-ultrasound. The fetus is 2.0cm long, and there is a strong echo light group in the 2.1cm uterine horn. The diameter of the fetal eye is 0.19cm, the amniotic cavity is 3.90*2.52cm; the diameter of the uterine horn cavity is 7.92*4.36cm. The fetus is 2.5cm long, with a visible strong echo mass in the uterine horn, the amniotic membrane can be identified, and the cow ultrasound shows a strong echo halo.

The cow was pregnant for 41-45 days. The cow B-ultrasound was used for observation and measurement. The fetal length was about 2.79cm, and the cow fetal length was 3cm. The cow fetal outline was visible on the cow B-ultrasound image, the head and trunk were clearly segmented, and the head and trunk bones were strong echoes; the abdominal area was a gray echo area; the umbilical cord diameter was 0.46cm, the umbilical cord periphery was the second strongest echo, and the second strongest echo area and the anechoic liquid dark area were in turn inward; the cervix was clearly outlined and strong echo, and the internal cervical ring was clearly identifiable, with 2 rings, the cervical ring was the second strongest echo, mixed with a small amount of strong echo spots, and the anechoic liquid dark area was between the two rings. The internal and external openings of the cervix were strong echoes, and the vaginal vault was a weak echo area.

The cow was 46-50 days pregnant, and the cow B-ultrasound was used for observation and measurement. The fetal length was 3.58cm, the fetal outline was clear, the cranial cavity was dark, the trunk bones were discernible, the abdominal cavity was a weak echo area; the heart area was vaguely visible; the amniotic membrane was visible as a strong echo bright ring, the diameter of the amniotic cavity was 5.27*2.53cm; the diameter of the uterine cavity was 8.15*3.96cm. The echo of the stomach area was visible.

The cow was 61-65 days pregnant, and the cow B-ultrasound was used for observation and measurement. When the fetal length was 6.26cm, the fetal outline was clear, the brain diameter was 1.26cm; the orbital diameter was 1.21cm; the cotyledon diameter was 1.2cm; the umbilical cord diameter was 0.62cm; the amniotic membrane diameter was 9.48*5.1cm. The fetus is 6.5cm long, and the outline of the fetus is visible. The cranial cavity is a liquid dark echo area. The spine and some ribs are strong echoes, and the ovaries are clearly identifiable. The umbilical cord is strong echoes on both sides, and some are weak echoes in the middle, and the abdominal area is identifiable. The male reproductive organs are visible, the limb bones are strong and round, and clear, and the brain diameter is about 1.07cm.

The dairy cow was pregnant for 71-75 days. The cow B-ultrasound was used for observation and measurement. The fetus was 12.2cm long, the echoes of the limbs and trunk bones were significantly enhanced, the width of the ribs increased by about 0.4cm, the hoof was slightly dark, and the boundary with the limb bones was clearly identifiable. The boundary between the abdominal cavity and the surrounding tissues was clear, the stomach area was obviously weakly echoed, and the intestinal tract was vaguely visible with strong and weak intersecting echo rings. For more information, please refer to the application of cattle B-ultrasound in dairy cow production

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