Artificial insemination in rabbits

Antimicrobials in a rabbit semen extender: effects on reproduction

The use of fluoroquinolone antibiotics was legally restricted by the European Commission in March 2019. Since the extender for rabbit semen Galap® contained this antibiotic, it became necessary to modify it. The purpose of this study was to search for another  molecule, based on its antimicrobial activity and also on the conservation, motility and fertility of semen diluted with the new extender. Several bacterial strains were isolated from 10 poor-quality ejaculates, including Enterococcus spp., Staphylococcus aureus and Proteus spp. They were then tested for antimicrobial susceptibility. Out of 15 antibiotics evaluated, gentamicin was the one targeting such bacteria. In vivo tests were then carried out to assess the effects of this antibiotic change on sperm parameters. Up to 26 pools of good quality semen (total motility >70%) were diluted in original Galap® or in this extender with gentamicin. Ejaculates were analysed on the day (D) of collection and up to 6 d of storage at +17°C. After 24 h storage, the motility in the new extender was reduced by 7.7% compared to the original; this decrease did not worsen by storing. After 6 d of storage, no difference between the two media was detected. A total of 360 females were then inseminated with pools of 4 to 5 good quality semen diluted 1:10 in both extenders, following the routine protocol of rabbit semen processing centres. There was no difference in female fertility or prolificacy between both formulations. In conclusion, these preliminary results suggest that the addition of gentamicin to this extender is useful andalso has no adverse effect on fertility or prolificacy.

Osmotic tolerance of rabbit spermatozoa is affected by extender composition and temperature

Sperm osmotic adaptability to anisosmotic conditions is important for sperm epididymal maturation, motility activation at ejaculation, and female tract colonization, or for conducting technological procedures such as cryopreservation. Several factors affect this adaptability, including the fluid composition that contributes to water flow dynamics, and the temperature at which osmotic stress is initiated. This study was designed to investigate the effect of medium composition (electrolyte- or sugar-based extender) and temperature (25 and 5 °C) on rabbit sperm adaptability to anisosmotic conditions. Rabbit spermatozoa, therefore, were diluted at both temperatures (25 and 5 °C) in electrolyte- or sugar-based media at increasing osmotic conditions (100 to 1,000 mOsm/kg), and values for sperm variables (sperm kinetics, membrane integrity, mitochondrial membrane potential) were estimated as endpoints. Sperm kinetics seemed to be more sensitive to osmotic stress than membrane integrity or mitochondrial function. The effect of moderate hypoosmotic stress did not differ when there was use of sugar- and electrolyte-based extenders at 25 °C (P > 0.05). In hyper-tonic conditions at 25 °C, the sugar-based extender was more effective in protecting sperm membrane integrity and mitochondrial function (P < 0.05). The lesser temperature made the differences more relevant because of the detrimental effect of hyperosmotic stress was more evident in the electrolyte-based extender at 5 °C (P < 0.05). The results from this study indicated rabbit spermatozoa have different adaptability to anisosmotic conditions induced by sugar- and electrolyte-based media and that the temperature at which the osmotic stress is initiated affects the cellular response.

The capability of coenzyme Q10 to enhance heat tolerance in male rabbits: evidence from improved semen quality factor (SQF), testicular oxidative defense, and expression of testicular melatonin receptor MT1

Heat stress (HS) has a great influence on the etiology of male infertility. Coenzyme Q10 (CoQ10), known to have powerful antioxidant effects, has been reported to have such actions that are effective to treat infertility caused by HS. The aim of the present study was to investigate the antioxidative effect of CoQ10 on sperm quality, testicular antioxidant activities, and male fertility under HS. For this purpose, 18 mature male rabbits (aged 22 wk) of the Sinai Gabali breed were equally divided into 3 groups and placed at temperature-humidity index of 29 for 8 wk at a farm. The supplementation of CoQ10 at 0, 10, and 20 mg/kg of body weight was done in the first, second, and third groups, respectively. The results showed that the supplementation of CoQ10 had significant (P < 0.05) effect on semen quality factor (SQF) and testicular antioxidant activities by the supplementation of CoQ10. Moreover, a significant improvement in the concentration of testosterone, integrity of testicular DNA, and the expression of melatonin receptors was also observed, which were consistent with a significant improvement in buck fertility. The prolificacy was significantly increased (P < 0.05) in females when inseminated from bucks that were treated with CoQ10. Our results suggest that CoQ10 tends to decrease oxidative stress by enhancing testicular antioxidant activities, which are considered the most important factors for a buck's fertility. Hence, CoQ10 could be a suitable feed supplement to increase fertility, through enhancing the semen quality, in male rabbits and reducing the harmful effects of HS.

Comparison between Tris-buffer and INRA-82 extenders on the quality of chilled rabbit spermatozoa

<p>The aim of the present study was to compare the effects of tris-buffer and INRA-82 extenders on the quality of cooled rabbit spermatozoa. Pooled semen samples were collected from eight New Zealand White rabbit bucks, divided into three groups and diluted 1:5 with three different semen extenders: INRA-82, tris-citrate glucose (TCG) and tris-citrate trehalose (TCT). Following dilution, the samples were stored at 5°C for up to 48 h. Sperm motility was recorded at 24, 36 and 48 h post-cooling. Furthermore, sperm viability, morphology, membrane integrity, acrosome status and DNA integrity were assessed at 24 h post-cooling. We found that progressive motility percentages were significantly higher (<em>P</em>&lt;0.05) in samples diluted in INRA-82 (61.00, 53.50, 44.00% at 24, 36 and 48 h post-cooling, respectively) than those diluted in either TCG (39.25, 32.00, 19.75%) or in TCT (47.25, 40.50, 29.00%). We also reported that sperm viability, percentage of normal spermatozoa, percentage of spermatozoa with intact acrosome and DNA integrity after 24 h cooling were significantly higher (<em>P</em>&lt;0.05) in INRA-82 diluted samples compared to TCG and TCT diluted ones. In summary, our results show that dilution of rabbit semen in INRA-82 improved sperm physiological parameters post-cooling compared to those diluted in TCG or TCT. Our findings also suggest that INRA-82 is a promising diluent that can be used effectively to maintain the viability of chilled rabbit semen.</p>

Silk protein sericin pretreatment enhances osmotic tolerance and post-thaw sperm quality but reduces the ability of sperm cells to undergo in vitro induced acrosome reaction in rabbit

Effect of sericin pretreatment of sperm cells on the osmotic tolerance, ability to undergo acrosome reaction induced by calcium ionophore (CI), heparin (H) or lysophosphatidylcholine (LPC), post-thaw sperm quality and in vivo fertility was evaluated in four successive experiments in rabbit. In experiment 1, fresh semen was pretreated with sericin (0, 0.1% or 0.5% w/v) before exposing to fructose solutions adjusted to either 50, 100, 290, 500 or 1000 mOsm/L. Sericin pretreatment increased sperm livability in addition to live-membrane intact and total membrane intact sperm rates (P < 0.05) in 50 and 290 mOsm/L groups. In experiment 2, sperm samples were pretreated by either 0.1 or 0.5% sericin after removal of the semen plasma. CI, H or LPC were used to induce acrosome reaction in pretreated sperm samples. Sericin pretreatment, reduced the ability of sperm cells to undergo acrosome reaction (P < 0.05) in vitro. In experiment 3, ejaculates were frozen with or without sericin pretreatment in DMSO-sucrose extender. In post-thaw samples sericin pretreatment improved total and progressive motility, livability, membrane and acrosome integrity in a dose dependent manner (P < 0.05). In vivo fertility trials by artificial inseminations revealed contradictory results in experiment 4. Although 0.5% sericin pretreatment totally inhibited fertility, 0.1% sericin provided high pregnancy rates. In conclusion; sericin pretreatment enhances osmotic tolerance and post-thaw sperm quality, but reduces the ability of rabbit sperm cells to undergo in vitro induced acrosome reaction, but this effect is restored in vivo by dose dependent manner.

Culture of Preimplantation Rabbit Embryos

It is surprising that so little attention is currently given to in vitro culture of preimplantation rabbit embryos, even though the rabbit is the only laboratory animal in which there is very considerable embryo growth before implantation, resulting in a 300-fold increase in protein content of embryonic cells during the preimplantation period and the formation of more than a 100,000 cells in the blastocyst. This growth pattern explains why blastocyst formation in vitro has an absolute requirement for amino acids, and vitamins, particularly inositol, are esssential for blastocyst growth. A semi-defined medium supplemented with 1.5% BSA (variously known as BSM II or modified F10) was developed at Cornell University at the end of the 1960s and allowed the systematic investigation of the requirements for development of 1-cell rabbit embryos to blastocysts. However, the requirements for in vitro blastocyst growth comparable to in vivo growth still remain an unsolved problem. Citrate, often found as a contaminant in serum albumin, may have an essential role in rabbit blastocyst growth, which would fit in with its role in the development of serum-free media for culture of various types of mammalian cells.A comprehensive account of the methodology is given to enable a researcher with experience culturing embryos of a different species to work on the rabbit embryo. This account covers medium preparation, hormonal stimulation of superovulation, natural breeding/artificial insemination, and collection of embryos of different stages from 1-cell to blastocyst either after euthanasia or under anesthesia. Peculiarities of the rabbit embryo such as the presence of the mucoprotein coat and its effects on behavior of cultured and transferred embryos are described. Suggestions are made for future avenues of research.

The effect of bovine serum albumin and fetal calf serum on sperm quality, DNA fragmentation and lipid peroxidation of the liquid stored rabbit semen

The aim of the present study was to determine the effects of the bovine serum albumin (BSA) and fetal calf serum (FCS) on sperm quality, DNA fragmentation and lipid peroxidation of liquid stored rabbit semen stored up to 72 h at 5 °C. Ejaculates were collected from five New Zealand male rabbits by artificial vagina and pooled at 37 °C following evaluation. Each pooled ejaculate was split into three equal experimental groups and diluted to a final concentration of approximately 40 × 10(6)sperm/ml (single step dilution), in an Eppendorf tube, with the Tris based extender containing BSA (5mg/ml), FCS (10%) or no additive (control) at 37 °C, cooled to 5 °C and stored for up to 72 h. The extender supplemented with BSA and FCS did not improve the percentages of motility and acrosomal abnormality during 48 h compared to the control. The additives BSA and FCS had a significant effect in the maintaining of plasma membrane integrity between 48 and 72 h storage period, compared to the control (P<0.01). The supplementation of BSA and FCS had a protective effect on motility (P<0.05), plasma membrane integrity (P<0.01) and acrosomal integrity (P<0.01) at 72 h compared to the control. The supplementations with BSA and FCS led to a reduction in DNA damage of rabbit sperm at 48 and 72 h during storage period, compared to the control (P<0.001). Although supplementation of BSA and FCS caused significant (P<0.01) decreases in malondialdehyde (MDA) level at 48 h and 72 h, they significantly (P<0.01) increased the glutathione peroxidase (GPx) antioxidant activity up to 72 h when compared to the control group. In conclusion, BSA and FCS supplementation to liquid stored rabbit semen provide a protection for spermatozoa against cool storage-induced DNA damage and plasma membrane integrity by their antioxidative properties.

Artificial fertilization in rabbits by intracytoplasmic sperm injection (ICSI)

Intracytoplasmic sperm injection (ICSI) consists of the injection, under microscopic observation, of a single spermatozoon directly into the cytoplasm of an oocyte using an injection capillary. This technique is used commonly in human medicine in cases of infertility. The advantage of ICSI is that the technique requires only one spermatozoon per oocyte for fertilization. Spermatozoa used for ICSI do not require high motility; ICSI works as long as the sperm nucleus is genetically intact. This protocol describes methods for performing ICSI in rabbits using either fresh or frozen/thawed sperm.

The rabbit (Oryctolagus cuniculus): a model for mammalian reproduction and early embryology

The rabbit is a valuable animal model for a variety of biomedical research areas including in vitro fertilization, early embryology and organogenesis, neurophysiology, ophthalmology, and cardiovascular research. The rabbit is also used as a model for toxicology studies and analyses of drug effects on embryo and fetal development, as well as for research involving the immune system (e.g., host/pathogen interactions, asthma, arthritis, systemic lupus erythematosus). The rabbit’s most prominent use as a laboratory animal is antibody production; most biomedical research institutions thus provide the infrastructure and veterinary expertise for keeping rabbits. This article discusses current advances in applying modern life science research methods to basic and applied embryological research using the rabbit as a model for early intrauterine development in mammals, including state-of-the-art genomic tools and the sequencing data available (and planned) for the rabbit.