Ultrasonography of the ovaries and uterus and grey scale analysis of the endometrium during embryonic diapause in European roe deer

Knowledge about the mechanisms of embryonic diapause in European roe deer Capreolus capreolus (Linnaeus, 1758), although first described 140 years ago, is not extensive. In contrast to post mortem publications, this is an in-vivo study which monitored individual ovarian and uterine dynamics during diapause by transrectal ultrasonography. Ten roe deer were examined at 4 to 6-week intervals starting from the end of the breeding season (August) until after implantation (January), Sonographic appearance of corpora lutea and their average number observed per animal did not differ between pregnant (3.6) and non-pregnant (3.2) does prior to implantation. However, in pregnant animals (n = 5) endometrial changes associated with embryonic diapause were identified. The endometrium in pregnant does were low in echogenicity compared to the non-pregnant. Changes in echogenicity of the endometrium were first detected three months before implantation. Observed endometrial changes were quantified by computer-assisted grey scale analysis. Mean medians of grey scale histograms were lower in pregnant compared to non-pregnant animals beginning as from October. In late December and January, embryonic structures were detected in animals in which a low echogenic endometrium had been observed earlier. Ultrasono­graphy and grey scale analysis characterised efficiently the dynamic processes in the uterus and ovary during embryonic diapause in pregnant and non-pregnant roe deer.