The Position of the Abomasum in the First Six Weeks After Calving

In the highly pregnant cow the abomasum is forced to the cranial and ventral part of the abdomen by the gravid uterus. After calving, the abomasum is located at the left ventral part of the abdominal cavity. This mechanism is assumed to be one of the factors contributing to the pathogenesis of abomasal displacement (AD).

In the present investigation, the changes of the position of the abomasum were studied in 6 Holstein-Friesian cows by transabdominal ultrasonography in the first 6 weeks after calving. The position of the abomasum was determined via measuring the distance between the abomasal wall being visible by examination of the left abdominal wall and the ventral midline. (The precision of this measurement had been determined earlier by examination of 5 additional cows in intervals during a 24-hour period). Samples of rumen juice were taken via a Sørensen-Schambye probe for determination of the pH-value and the osmotic pressure.

The reproducibility of the measurements was determined via calculating the coefficient of variation. The position of the abomasum in relation to the number of days post partum, feed intake and the pH-value and osmotic pressure of the rumen fluid was estimated via regression analysis. After the analysis, a backward stepwise linear regression was performed to determine combined influences on the position of the abomasum.

A circadian, diurnal variation was observed in the position of the abomasum. After correcting for the circadian variation, a 0,136 coefficient of variation was determined for the method of measurement of the position of the abomasum.

With respect to the left body wall, the position of the abomasum was highest in the first days after calving; the height declined during the following weeks. The abomasum was found to form a blind pocket near the left body wall.

Feed intake, pH-value and osmotic pressure of rumen juice influenced the position of the abomasum. After backward stepwise linear regression the influence of the feed intake was not significant, since feed intake was closely related with the number of days postpartum.

The results show that ultrasonography is a good non-invasive method for determining the position of the abomasum. Measurements of the position of the abomasum are reproducible. The presence of a blind pocket formed by a part of the abomasum is more evident when the organ has a high position. There is a relation between the number of days after calving, pH-value and osmotic pressure of the rumen juice and the position of the abomasum.

These findings support the hypothesis that the shift of the abdominal organs after calving could form an important factor in the pathogenesis of AD. The presence of the abomasum on the left side of the abdominal cavity after calving and the declining height with time could explain why AD to the left side preferentially occurs within the first weeks after calving.