Evaluation of crystallisation structures of cervical mucus in Zwartbles sheep with previous oestrus synchronisation

This study was conducted to determine the individual types of crystallisation structures of cervical mucus (arborisation phenomenon) in sheep and changes in the types of these structures during oestrus. A total of 80 ewes aged between two and eight years were included in the study. Oestrus synchronisation was performed using intravaginal sponges, and samples of cervical mucus were collected 55–57 h after the removal of intravaginal sponges and subsequently evaluated. The crystallisation structures of the cervical mucus of sheep exhibit the same sequence during oestrus as in cattle. The most frequently occurring types of crystallisation in the observed sheep included twig-shaped (33.33%), twig-shaped-clubmosses (24.00%) and clubmosses (14.67%). The least common type was fern frond crystallisation (1.33%). A statistically significant difference was found between the representation of individual types of crystallisation (P < 0.01). As with cattle, it is possible to use the evaluation of the crystallisation of cervical mucus to determine the optimum time for insemination, especially in groups of animals with previous synchronisation/induction of oestrus. Establishing the correct time for insemination or natural mating with a ram makes it possible to optimise breeding management and improve pregnancy rates, which are crucial in breeding these seasonally polyoestrous animals. Based on the results, it can be stated that insemination should take place 57+ h after the removal of intravaginal sponges and the application of hormonal treatments for oestrus induction and synchronisation (equine chorionic gonadotropin).