Transabdominal ultrasonographic evaluation of fetal well-being in the late-term mare and cow.

Abstract

In the equine practice, attempts have been made to examine the fetus in the second and third trimester of pregnancy but all of the available methods have limitations. Until now, transabdominal ultrasonography has been regarded as the most informative examination. This method allows us to measure fetal heart rate, fetal activity as well as the quality and quantity of the fetal fluids. A modified biophysical profile for horses was used by several researchers in the USA from the 1990s as a gold standard. However, it is not sensitive enough and, in the authors' experience, professionals can face difficulties during its application (e.g. for measuring aortic diameter and fetal breathing movements). In cows, this method was first used for this purpose by a Canadian research group in 2007. They reported that transabdominal ultrasound was promising but showed low sensitivity in this species. The present studies show that birth weight cannot be predicted from fetal aortic diameter measurement in cows as suggested by other researchers. Transabdominal ultrasound needs special equipment (2-3.5 MHz convex transducer) and basic ultrasonographic knowledge; however, we suggest that in most cases it can be performed with the dam placed in a stock and without shaving the examination area. The method provides useful information within 30-40 minutes, enabling the examiner to determine whether or not the fetus is alive and to recognise placentitis or twins. This technique also allows measuring the combined thickness of the uteroplacental unit, and the authors' ongoing study showed higher normal values in Lipizzaner mares compared to values in other breeds. In conclusion, with the help of advanced techniques, simple and low-cost methods should be developed for the evaluation of the pregnant dam and its fetus to assess fetal viability in the veterinary practice.