Computed tomography study of the fetal development of the dairy cow stomach complex.

In the fetal development of animals, critical physiological and anatomical events influence the long-term health and performance of the offspring. To identify the critical growth phases of the fetal bovine stomach, we used computed tomography imaging on 30 German Holstein fetuses to examine the fetal bovine stomach in situ. Computed tomography allows the study of diverse parameters such as the volume of the stomach chambers in situ without the need for sophisticated filling preparation techniques. The absolute volume, relative volume, and monthly volume increase of each stomach chamber were determined. Computed tomography was a reliable method for in situ examination of the fetal bovine stomach complex from the third month of gestation onward. It was able to detect an abnormal position of the abomasum in 2 fetuses. The crown-rump length of the fetuses studied ranged from 9.5 to 89 cm (from 2.2 to 8.3 mo of gestation). Over this timeline, the changes in the relative volumes of the ruminoreticulum and abomasum were inversely related. Until mo 5 of gestation, the relative volume of the ruminoreticulum increased steadily, whereas that of the abomasum decreased. Thereafter, the relative volume of the ruminoreticulum became gradually smaller, and that of the abomasum became larger; by mo 8, the abomasum was larger than the ruminoreticulum. All stomach chambers had large increases in volume over the gestation period and we observed differences in development patterns and volume changes of the individual stomach chambers over this period. The largest monthly volume increase of the stomach complex was between mo 4 and 5 of gestation. In this period, the volume of the ruminoreticulum increased 43.8 times, that of the omasum 38.9 times, and that of the abomasum 30.03 times. Between mo 5 and 6 of gestation, the abomasum had another growth spurt, with a monthly volume increase of 10.4 times. These 2 time points in the gestation period may be critical phases of fetal development that should be considered in the management of pregnant cattle.