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Background The wisent (Bison bonasus) is a species that has undergone a population bottleneck. Homozygosity is prevalent within the population and may have a negative impact on semen quality in wisent bulls. Semen samples containing a large amount of functionally and morphologically impaired or dead spermatozoa have lower tolerance for cryopreservation process. Such samples are prone to involve damage acrosomes, to produce and release reactive oxygen which negatively affects proper function of spermatozoas. It is a good practice to select intact and viable gametes before subjecting the sample to cryopreservation to improve the efficiency of this process. The aim of this study was to assess the ability of Percoll® density gradient centrifugation in order to improve the quality of wisent spermatozoa after cryopreservation. Spermatozoa samples were analysed with computer-assisted semen analysis system and flow cytometry. Results Percoll® density gradient centrifugation resulted in increased percentage of motile spermatozoa, higher proportion of spermatozoa with normal morphology and proper functionality but also in a significant reduction of the total number of gametes. Nevertheless, the concentration of frozen spermatoza was still sufficient for obtaining a few complete insemination doses suggested for cattle from each epididymis. Conclusions While creating a high-quality genetic reserve, for in vitro fertilisation purposes, eliminating detritus and improving the overall quality of samples is more important than total number of spermatozoa. For these reasons, the achievement of higher post thaw quality of spermatozoa justifies the purification of samples by centrifugation in a Percoll® density gradient prior to the cryopreservation process.

With the exception of the domestic cat, all felid species (Felidae) are currently threatened with extinction in their natural habitat. To develop effective and optimal wild cat conservation programmes with assisted reproductive technology (ART) it is necessary to combine advances from different disciplines of science, starting from the biology of the species, through research into the population and habitat, assisted reproductive technologies, establishment of gene banks, developing bioinformatic systems, and ending with biodiversity and endangered species management. In the last few years knowledge of felid reproduction has expanded considerably thanks to comparative studies utilising the domestic cat as a research model for endangered wild cats. Basic reproductive techniques utilised in both domestic cat breeding and rescuing wild felid populations that are threatened with extinction include semen collection and cryopreservation, artificial insemination, oocyte collection, in vitro maturation, in vitro fertilisation, somatic cloning, and embryo transfer. The main directions in which assisted reproductive technologies are being developed in wild cat conservation implementations and the contribution of Polish research centres in advancing these methods are presented.

Although purebred cat breeding is growing in popularity in European countries, most research and publications concern dog reproduction. Infertility in queens has been poorly studied. It may not come as a surprise as common domestic shorthair cats are well known for their excellent fertility. However, even in the latter, the infertility rate is around 20%. Only recently, published articles have analyzed the reproductive performances in different breeds, for example in UK, Sweden, France and Italy, and found similar figures. In cats, infertility may arise from many factors such as mismating, prolonged anestrus or silent heats, hormonal, nutritional, genetical or chromosomal causes. Also, infectious diseases, probably frequent in breeding facilities, include pathological agents that are well recognized as having a negative effect on pregnancy or other pathogens for which the involvement in fertility problems is unclear. However, analyzing the literature, it appears that the most prevalent causes of infertility in pedigree cats may well be, in females, uterine pathology (sub-clinical endometritis, cystic endometrial hyperplasia, or mucometra), and in males, teratospermia, which may be “permanent” and linked to reduced heterozygosity or “transient” in tomcats that present normal quantitative spermatogenic parameters. The influence of the breed is unknown. There is an urgent need to study the origin of infertility in purebred cats in order to improve the diagnosis and to develop treatments that may restore normal fertility in subfertile or infertile animals.