The time of the first ovulation depends on the sheep breed, feeding conditions, year season, length of lamb nursing and following galactopoiesis. The objective of the present study was to analyse the follicle status after parturition in non-lactating Improved Valachian ewes. Laparotomy with following ovariectomy was performed after lamb weaning (spring) on days 17, 24 and 32 after parturition. The ovaries were USG analysed with 5.0 MHz linear and 7.5 MHz convex transducer. Follicular data were analysed quantitatively and qualitatively. The ovaries were collected at the end of laparotomy and fixed in 10% formalin. The sections of the ovarian tissue were stained with haematoxylin and eosin and Azan staining. Ovarian slides were microscopically studied and analysed by LUCIA-G ver. 4.71. The differences in the ovary size were not significant. The number of follicles < 3 mm monitored by USG on day 32 was higher than that on day 17 after parturition. The image analysis of the ovary sections showed significantly higher numbers in the total follicles (P < 0.05) and the follicles > 3 mm (P < 0.001). The rate of atresia was 82% and 89% on day 17 and on day 32 post partum, respectively. We observed single ovulation on day 17 and double ovulations on days 24 and 32 post partum. More than half of the total number of antral follicles visible on the ovary surface was prepared for recruitment and this number was higher on day 32 post partum. Follicle selection connected with a relatively low rate of atresia and responsible preovulatory follicle sizes opened the way for selecting more follicles for the dominance process and thus also for the occurrence of double ovulations.

Earlier we found that the puerperal period of ewes lambing in February was finished by day 34 post partum.The aim of this paper was to study the puerperal changes in ewes that lambed in September. Structural changes in the endometrium of the caruncular region were studied in 12 Slovak Merino ewes that lambed in September. The animals were killed on days 7, 17, 25 and 34 post partum. Samples were taken from the caruncular region of their uterine horns. The tissue samples were fixed, dehydrated and embedded in paraffin, and 7-10 mm sections were stained with hematoxylin-eosin. Microscopic analysis was performed using a projection microscope. Simultaneously the collected material was stained with toluidine-blue, and examined on the semi-thin sections. The epithelium above the caruncles was entirely destroyed on day 7. Damaged mitochondria and dilated cisterns of the endoplasmic reticulum were found in the electron micrographs. On day 17, the epithelium covered gradually a sizeable caruncle. The glandular epithelium was considerably degenerated. The caruncle was markedly reduced on day 25, and the endometrium was covered with epithelium. The endometrium was totally covered with epithelium, and cellular ultrastructure was no more damaged on day 34 post partum. The study of micromorphology of endometrial structure in caruncular area revealed that also in ewes that lambed in September, the puerperium is finished by day 34 post partum. Its course and timing did not differ from that seen in ewes lambing in February. The results extend the knowledge of the puerperal changes in different season of the year. Caruncular region, endometrium, ewe, histological structures, post partum, season of the year One of the factors that may unfavourably affect fertility is the course of the involutional and reparatory processes of the uterus in the postpartal period. At the onset of postpartal reproductive activity it is necessary to take into account the breed, the season of the year, nutrition, and the length of suckling (Kudláã 1985; DoleÏel 1989). The macroscopic changes occurring during involution of the sheep uterus were reported by Foote and Call (1969); Crowder et al. (1982); Botha (1976); Van Wyk et al. (1972); Krajniãáková (1990); Greyling and Van Niekerk (1991) in goat, and Massányi (1996) in rabbits. A comprehensive histological study of the sheep uterus post partum was carried out by Uren (1935); and Van Wyk et al. (1972) who found that the involution process of the uterus was completed by day 28 post partum. Botha (1976) reported that both the season and lactation influence epithelisation of the caruncles. The author observed sheep that lambed during the out-of-mating season (August) to have epithelisation in the caruncular region finished on day 34 post partum whereas those that lambed in the lambing season (March) on day 30 post partum.

Hredzák, R., A. Ostró, I. Maraãek, J. Kaãmárik, V. Îdilová, J. Veselá: Influence of Slow-rate Freezing and Vitrification on Mouse Embryos. Acta Vet. Brno 2005, 74: 23-27.The aim of the study was to compare the effect of two different methods of embryo freezing (slow-rate freezing employing programmable freezing equipment and ultra-rapid freezing by vitrification) on developmental capacity of two-cell mouse embryos on the basis of their development to blastocyst stage and implantation rate of blastocysts. Two-cell embryos were obtained from superovulated female mice and divided to three groups. The first group of embryos was frozen by the slow controlled-rate method using a programmable freezing equipment with propanediol as a cryoprotectant. Embryos from the second group were vitrified employing ethylene glycol as a cryoprotectant. The third group of embryos was cultivated in vitro without cryopreservation in a cultivation medium in an atmosphere of 95% air and 5% CO 2 . After thawing, the embryos from the first two groups were cultivated in vitro under conditions identical to those used for fresh embryos. The blastocysts that developed in vitro from embryos of all three groups were transferred to uteri of pseudo-gravid female mice to determine their implantation capacity. The percentage of vitrified embryos that developed into blastocysts was significantly lower than that of the fresh and slow-rate frozen embryos. The morphological appearance of embryos from all three groups was the same. The implantation rate of blastocysts that developed from vitrified embryos was significantly lower compared to the fresh and slow-rate frozen embryos. The results obtained indicate that freezing of embryos affects negatively their further development the negative effect of vitrification being more detrimental. As a "universal" vitrification protocol has not yet been defined, additional studies are needed to achieve its optimisation.

The aim of this work was to characterize the structural changes in the surface epithelium and endometrial glands as well as oviduct mucosa in goats after parturition using the light and transmission electron microscopy. Fifteen Slovak short-haired goats were used. They were killed on days 3, 21, 36, and 40 after parturition. The evaluation of semithin sections from day 3 postpartum revealed impaired epithelial cells. Lymphocytes and neutrophil granulocytes were present in the lumen of uterine glands. Ciliated cells and sporadic secretory cells that were released into the oviduct lumen were found on semithin sections from the ampullary part of oviducts (day 3 postpartum). Cells in the cytoplasm contained mitochondria and cisternae of endoplasmic reticulum. Impaired cells with a vacuolised cytoplasm were present on ultrathin sections from the caruncular region of endometrium on day 21 postpartum. Uterine glands were in the stage of proliferation. Ultrathin sections from day 21 postpartum showed that ciliated cells were present and secretory cells with secretory granules increased in the epithelium of oviduct ampulla. The surface epithelium on day 36 was continuous, simple columnar; in some locations pseudostratified columnar. No signs of morphological damage of cells were found. On the free border of ciliated cells of the oviduct mucosa on day 36, the presence of numerous kinocilia was observed. Glandular cells contained a great amount of dense secretory granules in the cytoplasm (day 36 postpartum). The microscopic and submicroscopic appearance of the uterus and oviduct on day 40 postpartum was similar to that on day 36 of the period observed. The results obtained can be used in synchronization or induction of estrus in the intensification of reproduction and increasing the reproductive turnover in goat husbandry. , uterus, oviduct, puerperium, light and electron microscopy Goat

The aim of the study was to determine the relationship between the rate of cooling of eight-cell mouse embryos to the temperature of liquid nitrogen (-196 °C) and their developmental capacity after thawing on the basis of their ability to leave the zona pellucida ('hatching') during in vitro culturing. Eight-cell embryos were obtained from superovulated female mice and divided into three experimental and one control group. Embryos from the experimental groups were cryopreserved by the vitrification method using ethylene glycol as cryoprotectant. The vitrification protocols used in the study differed in the rate of cooling of the cryoprotectant solution. Embryos from the first group were frozen in conventional 0.25-ml plastic straws, those from the second group in pipetting 'tips', and embryos from the third group, placed in vitrification solution, were introduced dropwise directly into liquid nitrogen. The control group of embryos was cultured in vitro without freezing in a culturing medium in an environment consisting of 95% air and 5% CO 2 . The developmental capacity of thawed embryos was assessed on the basis of their ability to leave the zona pellucida ('hatching') after three days of in vitro culturing. In the control group 95.1% of embryos 'hatched'. A significantly higher number of embryos that 'hatched' after thawing was observed in the group introduced dropwise directly into liquid nitrogen (60.0%) compared to the group frozen in pipetting 'tips' (37.9%). The group frozen in straws yielded significantly the lowest proportion of 'hatching' embryos (8.1%). These results showed that increasing cooling rates during vitrification of embryos improved their survival.