Post-thaw viability of bull AI-doses with low-sperm numbers

Effect of over dilution of semen with tris extender on motion and functional attributes of bull spermatozoa during cryopreservation

The present study was aimed to evaluate the effect of over dilution of semen with tris extender on motion and functional attributes of bull sperm post-thaw. Ejaculates (n = 24; mass motility ≥3+) were collected from bulls (n = 4) using artificial vagina, diluted to 20, 15, 10 and 5 million spermatozoa/0.25 ml, and cryopreserved. The results revealed that total motility (%), progressive motility (%) and rapid motility (%), straight linear velocity (μm/s), straightness (%) reduced significantly (p < 0.05) when semen was diluted to 5 million sperm concentration. Among the various sperm function attributes, proportions of live spermatozoa, acrosome intact spermatozoa, hypo-osmotic swelling responsive spermatozoa and non-capacitated spermatozoa reduced (p < 0.05) in 5 million spermatozoa, and the proportions of moribund spermatozoa, dead spermatozoa, live acrosome reacted spermatozoa, dead acrosome intact spermatozoa, capacitated spermatozoa and spermatozoa with lipid peroxidation increased significantly (p < 0.05) when semen was diluted from 20 to 5 million. However, the over-dilution of semen did not affect slow motility, dead acrosome reacted spermatozoa, sperm protamine deficiency and spermatozoa with lipid peroxidation. In conclusion, the over dilution of semen affected sperm motion and functional attributes of frozen-thawed bull semen.

Cholesterol-loaded cyclodextrin attenuates dilution effect and improves quality of bovine low sperm insemination doses during cryopreservation

In the present study, the effect of cholesterol-loaded cyclodextrin (CLC) on the quality of low sperm doses at post-thaw was evaluated. Twenty four ejaculates (6 from each bull) were collected and split into eight aliquots. First four aliquots were diluted up to 20-, 15-, 10- and 5-million sperm/0.25 ml, and remaining four were treated with CLC at the rate of 1 mg/120 million spermatozoa, followed by dilution up to 20-, 15-, 10- and 5-million sperm/0.25 ml. The diluted semen was equilibrated, cryopreserved and evaluated post-thaw. The averages of total motility, progressive motility, average path velocity, straight linear velocity, membrane intact spermatozoa and noncapacitated spermatozoa were higher (p < .05) in CLC-treated sperm doses compared to control ones. However, the moribund spermatozoa, capacitated spermatozoa and acrosome-reacted spermatozoa were reduced (p < .05) in CLC-treated spermatozoa compared to control. The curvilinear velocity and linearity did not differ (p > .05) between control and CLC-treated sperm doses. In conclusion, treatment of spermatozoa with CLC at the rate of 1 mg/120 million spermatozoon attenuates the dilution effect and improves the quality of bovine low sperm insemination doses during cryopreservation; hence it could be a favourable cryoprotectant for preserving bovine semen at higher dilutions.

Effects of different ultrastructures of lecithin on cryosurvival of goat spermatozoa

This study was to evaluate the effects of two different ultrastructures of lecithin including nanoparticles (NPE mostly nanomicelles) and lecithin nanoliposome (NLE) with egg yolk extender (EYE) on goat sperm cryopreservation. Semen samples were collected from 6 goats, then pooled, diluted and then frozen. Motility and motion parameters, plasma membrane integrity and functionality, morphology, apoptosis status (Annexin V-PI), acrosome integrity, DNA fragmentation and in vitro fertilisation were assessed. Total motility and most motion parameters were higher in EYE (p < .05) compared with the two lecithin extenders, while there were no significant differences between NLE and NPE. NLE and NPE had higher values for viable spermatozoa (Annexin V-PI) (p < .05) compared with EYE. The highest value for dead spermatozoa was observed in EYE (p = .08). A higher percentage of DNA fragmentation (p < .05) was detected in EYE compared with NPE. Plasma membrane integrity and functionality, morphology, acrosome integrity and fertility of spermatozoa indicated no significant differences between extenders. Data suggested that ultrastructural changes of lecithin (micelles versus. liposome) could not improve the sperm cryosurvival of goat spermatozoa. Moreover, we cannot also claim that lecithin-based diluent supplies better protection compared with the egg yolk in goat.

Is addition or removal of seminal plasma able to compensate for the dilution effect of buffalo semen?

The present study aimed to compensate dilution effect using additional seminal plasma (SP) in conventional (80 million (M) spermatozoa/ml) dose and low spermatozoa/dose (8M spermatozoa/ml). We also attempted to confirm whether removal of SP before the extension of ejaculates affects post-thaw sperm quality of buffalo semen. For this, semen ejaculates (N = 15) were divided into four groups: control (CON), removal of SP by centrifugation (NSP), resuspension of the centrifuged semen pellet into SP (CEN) and extra supplementation of SP (ESP). All groups were diluted into two different semen doses to 20 and 2M spermatozoa/0.25 ml using tris egg yolk extender and subsequently cryopreserved. We found that neither addition nor removal of SP affected sperm motility, kinematics, longevity, mitochondrial superoxide production and high mitochondrial membrane potential (MMP). Further, the addition or removal of SP was not able to compensate dilution effect in 2M groups resulting in a significantly (p < .05) reduction in sperm motility, kinematics, sperm longevity, membrane integrity, MMP, and an increase production of mitochondrial superoxide. In conclusion, it appears that role of SP in the sperm cryopreservation process is insignificant.

Modification of French mini-straw plug position for cryopreservation of small doses of bull sperm

Greater than optimal diluting of semen for producing a large number of doses containing relatively small numbers of sperm can lead to compromised quality of sperm, post-thawing. In the present study the French mini-straw plug position was modified and the effect of re-positioning was evaluated on the quality of sperm after thawing subsequent to cryopreservation of small doses of sperm. Four types of mini-straws were used based on the position of cotton plug including no plug displacement (Type 1; Manufacturers location for plug-placement in 0.25 mL French mini-straws), and Type II, III, and IV with re-positioning the cotton plug being 2.5, 5, and 7.5 cm, respectively, further from the manufacturer's placement location. Each ejaculate was proportioned into four Aliquots (I, II, III, and IV) and diluted to 80, 60, 40, and 20, million sperm/mL, respectively. Aliquot I was placed in all types of straws, while Aliquots II, III, IV were placed only in Type I straws. Semen straws were equilibrated, cryopreserved and sperm kinetic and functional variables were evaluated post-thawing. The results indicate that in Aliquots III and IV there were lesser (P < 0.05) values for sperm kinetic and function variables compared with sperm from Aliquot I (i.e., unmodified mini-straw). In conclusion, cryopreservation of small doses of sperm in modified French mini-straws resulted in acceptable values for kinetic and function variables, post-thawing.

Alginate encapsulation preserves the quality and fertilizing ability of Mediterranean Italian water buffalo (Bubalus bubalis) and Holstein Friesian (Bos taurus) spermatozoa after cryopreservation

The use of artificial insemination (AI) in buffalo (Bubalus bubalis) is limited by poor ovarian activity during the hot season, seasonal qualitative patterns in semen, low resistance of sperm cells in the female tract, difficulties in estrus detection, and variable estrus duration. Although AI procedures are commonly used in bovine, use of AI has been limited in buffalo. In the zootechnical field, different studies have been conducted to develop techniques for improvement of fertilizing ability of buffalo spermatozoa after AI. In this study, for the first time, the use of alginate encapsulation and cryopreservation of buffalo spermatozoa is described, and the same procedure was performed with Holstein Friesian (Bos taurus) semen. Results obtained from in vitro analyses indicate that the encapsulation process does not have detrimental effects (compared to controls) on quality parameters (membrane integrity, progressive motility, path average velocity) in either species. Similarly, there were no detrimental effects after cryopreservation in either species. The fertilizing potential of encapsulated and cryopreserved semen was evaluated after AI in 25 buffalo and 113 bovine females. Pregnancy rates were not affected in either species. The results of this study show proof of concept for the use of frozen semen controlled-release devices in buffalo.

The Effect of Sperm Concentration and Storage Vessel on Quercetin-Supplemented Rabbit Semen During Chilled Storage

Extending the shelf life of chilled rabbit spermatozoa is vital for the expansion of the farmed rabbit industry. This study evaluated the relationship between sperm concentration and packaging on in vitro quality of chilled rabbit semen over 96 h. Semen was collected from adult bucks (n = 4) and pooled at 37°C following evaluation. Pooled ejaculates were diluted with a Tris-based extender supplemented with 100 μm quercetin to a concentration of 15, 30 or 60 × 10(6)  spermatozoa/ml, packaged into plastic tubes or 0.5-ml straws and stored at 15°C. Sperm quality was assessed by computer-assisted sperm Analysis [total motility (tMOT)] and flow cytometry [viability, acrosome integrity, H2 O2 production, plasma membrane disorder, apoptosis and DNA fragmentation index (DFI)] at 0, 48, 72 and 96 h. From 48 h, concentrations of 30 and 60 × 10(6)  spermatozoa/ml reported the highest tMOT, irrespective of storage vessel (p < 0.05). Storage in straws reduced oxidative stress and improved plasma membrane stability. The %DFI, mean DFI and SD-DFI were increased in spermatozoa stored in tubes compared with straws (p < 0.05). Although the use of low sperm concentrations in artificial insemination doses would facilitate greater dispersion of genetically superior rabbit bucks, dilution to 15 × 10(6)  spermatozoa/ml had a detrimental impact on motility. As such, chilled storage at 30 × 10(6)  spermatozoa/ml may provide a suitable balance between motility and H2 O2 production to best maintain overall sperm function and should be evaluated in a large-scale AI trial.

Assisted reproductive techniques for cattle breeding in developing countries: a critical appraisal of their value and limitations

Commercialization of animal biotechnologies, including those related to reproduction [also known as assisted reproductive techniques (ARTS)], is an increasing reality in developing countries, following the enormous flow of information around us and the increasing global commercial interests in areas where cattle production has its major assets. The present review discusses the achievements of various biotechnological tools for reproduction in cattle including semen handling for artificial insemination (AI), superovulation and embryo transfer (MOET), in vitro handling of oocytes and production of embryos, reproductive cloning and emerging technologies (sex selection, gene targeting and nuclear transfer for livestock transgenesis, genomics for marker-assisted selection, etc.). The application of these technologies for cattle breeding is critically discussed in relation to their impact in the improvement of the efficiency of dairy and beef production in developed and - particularly - in developing countries, which ultimately rule the possibilities of a competitive and sound production of food for human consumption. Despite the remarkable progress made and the punctual importance of some of the above-mentioned technologies, AI remains the most important assisted reproductive technology (ART) in developing countries. Any attempt to gain widespread of any other ART under the predominant economical conditions in developing countries ought to match the simplicity and the success of AI as a breeding tool.

Effect of low-density lipoproteins, spermatozoa concentration and glycerol on functional and motility parameters of bull spermatozoa during storage at 4 °C

An extender has been developed with low-density lipoproteins (LDLs) that eliminates the microbial risks associated with the use of whole egg yolk. The objective of this study was to assess the effects of substituting egg yolk with LDLs for use as an extender in sperm preservation at 4 °C, as well as on spermatozoa motility, plasma membrane and acrosome integrity, at two different concentrations (80×10(6) and 240×10(6) sperm per ml) for 8 days and to evaluate glycerol toxicity in both extenders. A total of 12 ejaculates were collected from three bulls. Spermatozoa motility was examined using computer-assisted semen analysis. Plasma membrane integrity was determined using the hypo-osmotic swelling test and acrosome integrity with the fluorescein isothiocyanate-Pisum sativum agglutinin test. The semen was subsequently divided into four aliquots and diluted with Tris-egg yolk-glycerol (TEG), Tris-egg yolk without glycerol (TE), LDL with glycerol (LDL(+)) and LDL without glycerol (LDL(-)), at 80×10(6) and 240×10(6) sperm per ml. This study showed that the LDL(+) and LDL(-) extenders were more effective at preserving spermatozoa motility, plasma membrane integrity and acrosome integrity than TEG and TE (P<0.05) during 8 days of incubation. After 3 days of incubation, a toxicity of glycerol was observed in TEG, whereas no significant difference was observed between LDL(+) and LDL(-). We can therefore conclude that the LDL extender can be used to refrigerate semen at 4 °C instead of TEG and TE at 80×10(6) and 240×10(6) sperm per ml for elite bulls. This finding can be used to define a policy for the storage of high-quality bull semen.

Improved quality of sex-sorted sperm: a prerequisite for wider commercial application

To date the only successful method to sort sperm into X- and Y-chromosome-bearing populations is the Beltsville Sperm Sexing Technology. Fertility results continue to be variable even though the technology has been used in a commercial setting for nearly a decade. This is at least partly due to the reduced lifespan of sperm after sorting and freezing. Several technical and biological factors are responsible for this problem. Furthermore, to meet economic demands, only 10-15% of the number of sperm (compared to unsexed semen) are loaded in each straw, further limiting the chances for fertilization. A new protocol for preservation of bull sperm, utilizing Sexcess shows promise in extending the lifespan of sorted bull sperm. Motility and acrosome integrity are significantly increased using Sexcess. Conception rates achieved with heifers for those bulls tested with Sexcess and using a standard AI regime give results that do not differ from results achieved using regular AI. In addition to the improvements of the sorting technology itself, we recommend a thorough pre-selection of bulls. A reliable prediction method to determine whether a bull is suitable for a sex-sorting program still does not exist. Such a test is needed, especially for "custom sorting" programs. Currently, test sorts are the only means of obtaining information about the sorting efficiency of semen from a particular bull.