In vitro sperm penetration through the zona pellucida of immature and in vitro matured oocytes using fresh, chilled and frozen canine semen

Comparing different sperm concentrations for optimizing cooled semen use in the dog

The use of shipping canine semen for artificial insemination has bloomed over the last 20 years. This allows for the spread of genetic material while overcoming geographical or time-related challenges. The optimal sperm concentration for cooled semen transport in the dog is unknown. Often canine semen is extended 1:3-5 vol:vol without standardized sperm concentrations for cooled shipment. We compared different sperm concentrations for cooled storage and hypothesized that lower concentrations would result in better semen quality. Semen was collected from healthy client-owned dogs (n = 8). Individual ejaculates were divided into a control aliquot (CON) extended 1:3 vol:vol with a commercial extender. The remaining sample was centrifuged and extended to 200 ×106 sperm/ml (C200), then serially diluted to 100, 50, and 25 ×106 sperm/ml concentrations (C100-C25). Aliquots were cooled for 24 h and then centrifuged and re-extended. Sperm concentration, plasma membrane integrity (PMI, %), motility (subjective total, STM; computer-assisted sperm analysis (CASA) total and progressive, TM, PM; %), and normal morphology (NM, %) were assessed in raw semen (T0), post-extension (T1), after 24 h of cooling (T2), and after processing at 24 h (T3). Cooling resulted in significant declines in STM and NM for all groups and in decreased PMI for CON and C25-50. After cooling (at T2), PMI was significantly lower for C25 compared with all the groups and higher for CON compared with C25-100 (p ≤ 0.038). Processing and re-extension after cooling further decreased the spermiogram parameters. At T3, PMI for CON was similar to C200 but significantly higher than C25-100, while C25 had the lowest PMI. For motility parameters and NM, C25 performed worse than all or most of the other groups. Comparing CON at T3 with C25-200 at T2, PMI, STM, and NM for CON were significantly lower than C25-200, C200, and C100-200, respectively. In conclusion, our results show that cooling canine semen for 24 h at 200 ×106 sperm/ml final concentration after processing or extending 1:3 vol:vol without centrifugation is preferred based on the highest PMI. If volume restrictions apply, processing raw semen and extending to the desired volume with higher sperm concentrations at the collection facility is superior to centrifugation and volume adjustment after 24 h of cooled storage.

Canid Reproductive Biology: Norm and Unique Aspects in Strategies and Mechanisms

The reproductive physiology of canids is unique compared to other mammalian species. Specifically, the reproductive cycle of female canids is characterized by extended periods of proestrus and estrus followed by obligatory diestrus and protracted ovarian inactivity (anestrus). Although canid reproduction follows this general pattern, studies have shown variations in reproductive biology among species and geographic regions. Understanding of these differences is critical to the development of assisted reproductive technologies including estrus induction, gamete rescue, and embryo production techniques for canid conservation efforts. This review summarizes current knowledge of canid reproduction, including estrus cyclicity, seasonality, and seminal traits, with the emphasis on species diversity. The application of reproductive technologies in wild canid conservation will also be discussed.

Evaluation of spermatozoal function-useful tools or just science

Conventional microscopic semen analysis does not provide precise information on the fertilizing potential of a male. The traditional basis for semen evaluation is that male fertility is dependent on production of a "proper" concentration/number of motile, morphologically normal spermatozoa in excess to achieve conception. Many independent studies, especially in human medicine, have demonstrated that the absolute number of spermatozoa does not accurately determine fertility, but their functional competence. Many functional tests of spermatozoa are developed over the last decades. Computer-assisted sperm analysis (CASA) and flow cytometry have become the gold standard for semen assessment in specialized andrology laboratories. Other functional assays, such as gamete interaction tests, provide additional information regarding the real fertilizing potential of sperm cells. From this point of view, such tests are valuable diagnostic tools in fertility disorders and may be helpful to make a decision which method of treatment to use: pharmacological therapy, intrauterine insemination, introduction of classic IVF, ICSI or exclusion from a breeding programme. The most useful gamete interaction tests include induced acrosome reaction, zona pellucida binding assay, oocyte penetration assay and hyaluronan binding assay. In recent years, andrology has entered into a new era of sophisticated OMICS methods. Genomics, epigenomics, transcriptomics and proteomics brought high hopes for rapid progress in clinical diagnostics.

Early embryonic development, assisted reproductive technologies, and pluripotent stem cell biology in domestic mammals

Over many decades assisted reproductive technologies, including artificial insemination, embryo transfer, in vitro production (IVP) of embryos, cloning by somatic cell nuclear transfer (SCNT), and stem cell culture, have been developed with the aim of refining breeding strategies for improved production and health in animal husbandry. More recently, biomedical applications of these technologies, in particular, SCNT and stem cell culture, have been pursued in domestic mammals in order to create models for human disease and therapy. The following review focuses on presenting important aspects of pre-implantation development in cattle, pigs, horses, and dogs. Biological aspects and impact of assisted reproductive technologies including IVP, SCNT, and culture of pluripotent stem cells are also addressed.

The canine oocyte: uncommon features of in vivo and in vitro maturation

The biology of the canine oocyte is unusual compared with that of other mammalian females. The present paper reviews both in vivo and in vitro specificities of canine oocytes. Final follicular growth in the bitch is characterised by an early appearance of LH binding sites in the granulosa, a high proportion of polyovular follicles and a preovulatory luteinisation, starting at the time of the LH surge. Through follicular fluid, preovulatory oocytes are thus exposed to high levels of progesterone, as high as 1000-fold plasma concentrations. The composition of the follicular fluid is affected by the size of the female. The more specific aspect of oocyte biology in the bitch is ovulation: oocytes are expelled immature, at the Prophase I stage. Ovulatory follicles are 6–8 mm in diameter, releasing oocytes from 110 µm, with dark cytoplasm. Resumption of meiosis occurs from 48 h postovulation, MII stages appearing 48–54 h after ovulation. The mechanisms controlling such a late meiotic resumption are still unknown. Granulosa cells seem to play a central role as in other mammalian species, but not with cAMP as the principal mediator. The importance of a transient reactivation of oocyte transcription a few hours before meiotic resumption is to be explored. These specific features may contribute to the low efficiency of IVM. Only 10–20% oocytes reach the metaphase stage and suffer from a poor cytoplasmic maturation. Moreover, in vitro culture of canine oocytes is associated with a high proportion of degeneration. To date, IVM of the oocytes is the main limiting factor for the development of assisted reproductive techniques in the canine. A better knowledge of the basic physiology of folliculogenesis and the molecular mechanisms controlling oocyte meiosis resumption in this species may allow us to overcome this obstacle.

Embryo biotechnology in the dog: a review

Canine embryos are a scarce biological material because of difficulties in collecting in vivo-produced embryos and the inability, to date, to produce canine embryos in vitro. The procedure for the transfer of in vivo-produced embryos has not been developed adequately, with only six attempts reported in the literature that have resulted in the birth of 45 puppies. In vitro, the fertilisation rate is particularly low (∼10%) and the incidence of polyspermy particularly high. So far, no puppy has been obtained from an in vitro-produced embryo. In contrast, cloning of somatic cells has been used successfully over the past 4 years, with the birth of 41 puppies reported in the literature, a yield that is comparable to that for other mammalian species. Over the same period, canine embryonic stem sells and transgenic cloned dogs have been obtained. Thus, the latest reproductive technologies are further advanced than in vitro embryo production. The lack of fundamental studies on the specific features of reproductive physiology and developmental biology in the canine is regrettable in view of the increasing role of dogs in our society and of the current demand for new biological models in biomedical technology.