Sonographic fetometry in the bovine.

The fetuses of 19 heifers were examined a total of 485 times during the course of pregnancy by means of transrectal sonography with sector scanners. Changes in size of organs and parts of the body were fetometrically assessed and the relative frequency of different intrauterine positions during pregnancy was registered. Until the end of Month 4 of gestation, anterior and posterior presentations occurred with equal frequency. During Months 5 to 7 the posterior presentation was found in about 25% of the cases, while after that it was rarely encountered at all. The head, thorax, abdomen and pelvis of the fetuses were readily accessible for transrectal sonography during the first 4 mo. During Months 5 to 7, the thoracic, abdominal and pelvic regions could be examined in at least one third of the cases. The head was accessible in about 80% of the cases examined throughout all stages of pregnancy. Ultrasound fetometry served to assess average growth-rate of a number of organs during pregnancy. The regressions and correlation coefficients between the development of bovine fetuses and the age of gestation were obtained for the following structures: eye, braincase, trachea, stomach, vena cava, urinary bladder, scrotum, ribs, cervical vertebrae, thoracic vertebrae, lumbar vertebrae, coccygeal vertebrae, scapula, humerus, radius and ulna, metacarpus, os ilium, os ischii, femur, tibia, metatarsus, trunk, crown-rump length and umbilical cord. Additionally, the development of the fetal heart rate during pregnancy was observed. It can be concluded that intrauterine development of the bovine fetus and its gestational age may be judged from the size of its organs and parts of the body.