Pregnancy and conception rate after two intravaginal inseminations with dog semen frozen either with 5% glycerol or 5% ethylene glycol

Evidence-based practice in canine artificial insemination

A number of methods are currently used to predict the optimal date of insemination of the breeding bitch, particularly with the use of frozen-thawed canine semen which has a far shorter lifespan than fresh semen. Aside from confirming cytological oestrus, vaginal cytology is of no assistance in predicting the most fertile day(s) in a bitch; however, a neglected avenue of research suggests that vaginal cytology may be of great importance in confirming the days of optimal fertility retrospectively. Similarly, vaginoscopy provides clues as to the stage of a bitch's cycle but is inadequate as a sole determinant of her most fertile days. Nevertheless, vaginoscopy is useful to identify very late oestrus and the onset of dioestrus, as well as Stage I of labour (cervical dilatation). Due to variations in the rate at which circulating progesterone concentrations rise in individual bitches, the reliability of circulating progesterone concentrations for determining the optimal day(s) of insemination with frozen-thawed semen decreases as values rise. Moreover, progesterone assay results can vary widely due to extrinsic factors such as the time of blood sampling, sample storage conditions and the assay employed. Finally, this review investigates evidence surrounding various insemination routes and suggests that well-performed vaginal insemination, even with frozen-thawed semen, may be an acceptable approach for cases where transcervical insemination is impractical.

Melatonin Supplementation for the Cryopreservation of Canine Sperm

Antioxidants can be used in sperm cryopreservation protocols to reduce oxidative stress that occurs due to the cryopreservation process. The aim of this study was to evaluate the effects of melatonin supplementation on quality and oxidative stress parameters in cryopreserved canine sperm. Eighteen sperm ejaculates were collected from 6 Frenchie Bulldog males (3 collections per male). Sperm motility parameters, membrane integrity, and sperm morphology were analyzed before the cryopreservation process. The extender used in cryopreservation was composed of Tris-egg yolk and ethylene glycol 5% was added as a cryoprotectant. The cryoprotective medium was supplemented with 1.0, 1.5, 2.0, 2.5, and 3.0 mM melatonin, and the control group (without melatonin). Post-thaw sperm was evaluated as described for fresh sperm and oxidative stress parameters (lipid peroxidation, catalase, and superoxide dismutase). Post-thaw sperm motility parameters, membrane integrity, sperm morphology, and oxidative stress parameters did not differ (p > 0.05) among the control group and samples supplemented with melatonin. The results of this study showed that melatonin supplementation had no positive or negative effect on the parameters evaluated. Thus, it is suggested that different concentrations of melatonin be tested to assess its effectiveness as an antioxidant in the cryopreservation process in canine sperm.

Assisted reproductive techniques for canines: preservation of genetic material in domestic dogs

Assisted reproductive techniques (ARTs), such as artificial insemination, in vitro fertilization, and cryopreservation of gametes/zygotes, have been developed to improve breeding and reproduction of livestock and for the treatment of human infertility. Their widespread use has contributed to improvements in human health and welfare. However, in dogs, only artificial insemination using frozen semen is readily available as an ART to improve breeding and control genetic diversity. A recent priority in sperm cryopreservation is the development of alternatives to egg yolk, which is widely used as a component of the sperm extender. Egg yolk can vary in composition among batches and is prone to contamination by animal pathogens. The latter can be a problem for international exchange of cryopreserved semen. Low-density lipoprotein and skim milk are promising candidates for use as extenders, to ensure fertility after artificial insemination. Although not tested for its effects on fertility following artificial insemination, polyvinyl alcohol may also be a useful alternative to egg yolk as an extender. The development of cryopreservation techniques for canine embryos lags behind that for other mammals, including humans. However, given the success of non-surgical embryo transfer in 2011, studies have sought to refine this approach for practical use. Research on sperm cryopreservation has yielded satisfactory results. However, investigation of other approaches, such as cryopreservation of oocytes and gonadal tissues, remains insufficient. Techniques for the efficient induction of estrus may aid in the development of successful canine ARTs.

Effects of the cryopreservation process on dog sperm integrity

Sperm cryopreservation has become an indispensable tool in reproductive biology. However, frozen/thawed semen has a short lifespan due to loss of sperm cell integrity. To better understand which sperm cell structures are compromised by the cryopreservation process and apoptosis markers, the sperm of five healthy mature dogs was analyzed in this study. Analysis was performed after collection, cooling, and thawing via computer assisted sperm analyzer (CASA) and evaluation of membrane fluidity and permeability, phosphatidylserine translocation (Annexin V), membrane integrity, mitochondrial membrane potential, membrane lipid peroxidation (LPO) and activity of the apoptotic markers caspases 3 and 7 by flow cytometry. Cryopreservation decreased total and progressive motility and the percentage of rapid sperm (P < 0.01). Damage to sperm cells was confirmed by Annexin V (P < 0.01), indicating that capacitation-like changes were induced by the cryopreservation procedures. An increase in sperm membrane fluidity was also noted in frozen/thawed samples (P < 0.01). Plasma and acrosomal cell membranes were affected (P < 0.01), with decreases in the subpopulation displaying high membrane potential (P < 0.01). Membrane LPO was increased in thawed sperm compared to cooled sperm (P < 0.05) but was not different from that in fresh sperm. No differences were observed in caspase 3 and 7 activity after cooling, freezing, or thawing. In conclusion, total and progressive motility, plasma membrane integrity and mitochondrial membrane potential suffered from the deleterious effects caused by cryopreservation, unlike the activity of caspases that remained stable during the freezing process.

Small animal reproduction: Scientific facts versus dogmas or unverified beliefs

Small Animal Reproduction is a rather recent topic in the field of Animal Reproduction. Although some continuing educational societies aim to improve the level of general knowledge, published scientific facts are still limited, and there are many hypotheses or affirmations that remain unverified or even sometimes dogmatic or empirical. Through examples, this article reviews the main causes that may sometimes challenge a veterinary practitioner faced with a dog or a cat presenting reproductive problems. It could be difficult to orientate the diagnosis or the therapeutic approach, not knowing if what is found in the literature is a scientific proof or just an unverified affirmation. This problem may result from the fact that there are still physiological processes that remain unclear, but also that some common beliefs are based on old studies that have not been repeated or verifiedIn addition, to make it more challenging to seek for the information, there are unverifiedaffirmations,unclear nomenclature, clinical conditions which have not been standardized in the literature, clinical conditions mostly described through case reports, lack of studies on specific topics, areas of small animal reproduction that have been neglected by researchers, contradictory data or even studies that lack objectivity. The growing interest for research in Small Animal Reproduction will probably reduce the gap between unverified beliefs and scientific facts.

Triplex doppler ultrasonography to describe the uterine arteries during diestrus and progesterone profile in pregnant and non-pregnant bitches of different sizes

Hemodynamics of uterine vascularization is modified throughout pregnancy to meet the increasing demand of the growing fetuses and triplex doppler ultrasonography is widely used in human medicine to study the uterine arteries and assess the fetal and placental conditions. The aim of our study was to confirm this observation in the bitch, to evaluate differences between bitches of different sizes and to study abnormal pregnancies. Forty-four bitches were monitored during the estrous period to determine ovulation and every 10 days from ovulation to 50 days post-ovulation: the resistivity (RI) and pulsatility (PI) indexes of the right uterine artery were measured as well as usual assessment of fetal development and follow up of the luteal function. Thirty-three out of forty-four bitches were pregnant, including 6 abnormal pregnancies (resorption of more than 10% of the embryos). We also divided them in four weight categories: 8 were small (<10 kg), 13 medium (10-25 kg), 13 large (>25-40 kg) and 10 were giant breeds (>40 kg). We observed that RI and PI decreased over time and were significantly lower for pregnant bitches compared to non-pregnant ones from 30 days post-ovulation. In contrast, RI and PI did not significantly vary with the size of the bitches and we could not determine a significant impact of abnormal pregnancies either. In conclusion, we found no significant difference related to the size of bitches in the RI and PI. The only significant difference between pregnant and non-pregnant bitches was observed from 30 days post-ovulation.

Use of polyvinyl alcohol as a chemically defined compound in egg yolk-free extender for dog sperm cryopreservation

The objectives of this study were to investigate the effects of polyvinyl alcohol (PVA) as a chemically defined compound in egg yolk (EY)-free extender by determining the appropriate concentration of PVA and the effect of pH adjustment in EY-free PVA extenders on dog spermatozoa. Spermatozoa (1 × 10⁸  cells/ml) were frozen with EY-free extenders supplemented with 0 (control), 0.025, 0.05, 0.1, 0.2 or 0.3 g/100 ml PVA. Sperm progressive motility (PM) was assessed immediately after thawing (IAT) and post-thaw incubation (PTI), while viability, acrosome integrity and reactive oxygen species (ROS) levels were evaluated after PTI. Additionally, spermatozoa were frozen using EY-free PVA extenders before pH adjustment (6.45) and after adjustment of pH (6.85). Viability, PM, ROS and gene expression (BCL2 and SMCP) were assessed. Supplementation with 0.05 g/100 ml or more PVA significantly increased PM compared to the control group in the IAT and PTI. Post-thaw incubation significantly increased sperm motility in all groups. The acrosome integrity in all PVA groups was higher (p < .05) than the control without an effect on ROS and viability. Adjustment of the pH to 6.85 improved (p < .05) sperm PM compared to the non-adjusted groups without affecting viability, ROS or expression of BCL2 and SMCP. We suggest that PVA supplementation in EY-free Tris extenders can effectively protect dog spermatozoa during freezing and can maintain higher motility and acrosome integrity. Adjustment of pH in EY-free PVA extenders can improve post-thaw sperm motility. Therefore, PVA can be used as a compound in EY-free extender for the cryopreservation of dog spermatozoa.

Estimated impact of multiple conceptuses per follicle on fecundity in the bitch

Multiple conceptuses from one follicle due to multi-ovular follicles or monozygotic twins inflate the ratio between the numbers of conceptuses and corpora lutea and possibly the effect ascribed to experimental treatment. The aim of this study was to estimate the impact of multiple conceptuses per follicle on fecundity in the bitch. The numbers of conceptuses and corpora lutea of 105 bitches originated from 7 published experimental studies and of 132 from ovariohysterectomies done in a private practice and a welfare organisation. Ninety five bitches, producing 597 conceptuses, had at least as many conceptuses as corpora lutea; 83 had as many, 10 had one more and 2 had 2 more. Bootstrap resampling on these 95 bitches let us to conclude that 12.6% of bitches are expected to produce more oocytes that are each capable of yielding a conceptus than the number of follicles that ovulate and that 2.35% of conceptuses are expected to be in excess of the number of follicles that ovulate. Applying the results of the current study to 2 earlier studies showed that multiple conceptuses from one follicle may, at maximum, have increased the effect ascribed to prostatic fluid by 0.022 and 0.024 conceptuses per corpus luteum, which is minor in relation to the magnitude of the ascribed effects of 0.34 and 0.22 conceptuses per corpus luteum. The number of conceptuses relative to the number of corpora lutea provides a valid and precise measurement of fertility in the bitch.

Oxidative stress at different stages of two-step semen cryopreservation procedures in dogs

Sperm cryopreservation generates sperm damage and reduced fertilization capacity as a consequence of reactive oxygen species formation. Identifying the critical points of the process will contribute to the development of strategies for oxidative stress prevention. Therefore, the aim of this experiment was to verify the occurrence of oxidative stress during the two-step cryopreservation process in dogs. Six healthy mature dogs were used and submitted to the two-step sperm cryopreservation protocol. The sperm analysis was done at three time points: after refrigeration, after glycerolization, and after thawing by sperm motility, measurement of spontaneous and induced oxidative stress, sperm mitochondrial activity, plasma membrane integrity, flow cytometric evaluation of plasma and acrosome membrane integrity, mitochondrial membrane potential, and sperm chromatin structure assay. There was an increase in free radical production after glycerolization (87.4 ± 15.5 ng/mL of spontaneous thiobarbituric acid reactive substances (TBARS) after refrigeration and 1226.3 ± 256.0 ng/mL after glycerolization; P < 0.05), in association with loss of sperm mitochondrial activity. However, frozen-thawed samples had lower sperm motility, lower resistance to oxidative stress (448.7 ± 23.6 ng/mL of induced TBARS after glycerolization and 609.4 ± 35.9 ng/mL after thawing; P < 0.05) and increased lipid peroxidation (4815.2 ± 335.4 ng/mL of spontaneous TBARS after thawing; P < 0.05) as well as increased damage to plasma and acrosomal membranes, compared with refrigeration and glycerolization. In conclusion, the production of free radicals by sperm cells begins during glycerolization. However, sperm oxidative damage intensifies after thawing. Despite intracellular ice formation during cryopreservation, the increased production of reactive oxygen species can be the explanation of the decrease in sperm motility, reduced mitochondrial activity, and sperm plasma membrane and acrosomal damage.

Maintaining canine sperm function and osmolyte content with multistep freezing protocol and different cryoprotective agents

Cryopreservation procedures cause osmotic stress to spermatozoa following cryoinjury and reduce their content of osmolytes. Conventional method for cryoprotectant loading and dilution on canine semen freezing which could be categorized in single step protocol, makes decreasing in sperm performance such as motility, morphology and viability. Therefore, the objective of the present study was to determine if a multistep protocol using glycerol or ethylene glycol can be used to overcome the osmotic sensitivity of canine spermatozoa, and to identify osmolytes that were involved in regulation of osmotic stress. A multistep protocol, comprising serial loading and dilution of cryoprotective agents by dividing the total volume of extender into 4 steps (14%, 19%, 27%, and 40%) every 30s, was compared to a single step method. Frozen-thawed spermatozoa in the multistep group showed superior quality (P<0.05) compared with the single step process in progressive motility (23.3 ± 1.3% vs. 12.5 ± 1.6%), intact membranes (66.5 ± 2.8% vs. 49.5 ± 2.6%) and bent tail (29.2 ± 3.2% vs. 46.2 ± 1.9%). Multistep also succeeded in minimizing loss of the osmolytes carnitine (20.6 ± 2.0 nmol/U G6PDH vs. 10.8 ± 2.1 nmol/U G6PDH) and glutamate (18.4 ± 1.6 nmol/U G6PDH vs. 14.4 ± 0.8 nmol/U G6PDH) compared to the single step group. Moreover, glycerol with multistep was more advantageous for maintaining sperm quality than ethylene glycol. In conclusion, the multistep protocol with glycerol can be used to improve the morphology, motility and osmolytes content of frozen-thawed canine spermatozoa.