Birth of female piglets following intrauterine insemination of a sow using flow cytometrically sexed boar semen

Gender Control of Mouse Embryos by Activation of TLR7/8 on X Sperm via Ligands dsRNA-40 and dsRNA-DR

Gender control technologies are promising for enhancing the production efficiency of the farm animal industry, and preventing sex-linked hereditary diseases in humans. It has been shown that the X sperm of mammalian animals specifically expresses X-chromosome-derived toll-like receptor 7/8 (TLR7/8), and the activation of TLR7/8 on the X sperm by their agonist, R848, can separate X and Y sperm via the specific inhibition of X sperm motility. The use of R848-preselected sperm for fertilization resulted in sex-ratio-skewed embryos or offspring. In this study, we aimed to investigate whether two other TLR7/8 ligands, double-stranded RNA-40 (dsRNA-40) and double-stranded RNA-DR (dsRNA-DR), are also effective in the separation of mouse X and Y sperm and the subsequent generation of gender-ratio-skewed in vitro fertilization (IVF) embryos. Our results indicated that cholesterol modification significantly enhances the transfection of dsRNA-40 and dsRNA-DR into sperm cells. dsRNA-40 and dsRNA-DR incubation with mouse sperm could separate X and Y sperm by the specific suppression of X sperm motility by decreasing its ATP level and mitochondrial activity. The use of a dsRNA-40- or dsRNA-DR-preselected upper layer of sperm, which predominantly contains high-motility Y sperm, for IVF caused a male-biased sex ratio shift in resulting embryos (with 65.90-74.93% of embryos being male). This study develops a simple new method for the efficient separation of mammalian X and Y sperm, enabling the selective production of male or female progenies.

Knockout of Rlim Results in a Sex Ratio Shift toward Males but Superovulation Cannot Compensate for the Reduced Litter Size

Technologies that can preselect offspring gender hold great promise for improving farm animal productivity and preventing human sex-related hereditary diseases. The maternal Rlim allele is required for imprinted X-chromosome inactivation, which is essential for the normal development of female mouse embryos. In this study, we inactivated the maternal Rlim allele in embryos by crossing a male transgenic mouse line carrying an X-linked CMV-Cre transgene with a female line carrying a loxP-flanked Rlim gene. Knockout of the maternal Rlim gene in embryos resulted in a male-biased sex ratio skew in the offspring. However, it also reduced litter size, and this effect was not compensated for by superovulation in the mother mice. In addition, we showed that siRNA-mediated knockdown of Rlim in mouse embryos leads to the birth of male-only progenies. This study provides a new promising method for male-biased sex selection, which may help to improve the productivity in livestock and prevent sex-associated hereditary diseases in humans.

Short-term storage of semen samples in acidic extender increases the proportion of females in pigs

Background

Sex preselection is a desired goal of the animal industry to improve production efficiency, depending on industry demand. In the porcine industry, there is a general preference for pork from female and surgically castrated male pigs. Therefore, the birth of more females than males in a litter leads to economic benefits and improved animal welfare in the pig production industry. Our previous study suggested that the porcine semen extender (BTS) adjusted to pH 6.2 maximises the differences in viability between X-chromosome-bearing (X) spermatozoa and Y-chromosome-bearing (Y) spermatozoa without affecting sperm’s functional parameters. In this study we aimed to evaluate whether the pH 6.2 extender is applicable at the farm level for increasing the number of female piglets without a decline in spermatozoa fertility. Artificial insemination (AI) was carried out with spermatozoa stored at pH 6.2 and pH 7.2 (original BTS) at day 1 and day 2 of storage. Next, the functional parameters of the spermatozoa, litter size, farrowing rate, and female-to-male ratio of offspring were determined.

Results

Although sperm motility decreased significantly after 2 d of storage, the viability of spermatozoa was preserved at pH 6.2 for 3 d. There was no significant difference in the farrowing rate and average litter size between the group inseminated with the spermatozoa stored in (pH 7.2) and that inseminated with spermatozoa stored in acidic BTS. The percentage of female piglets was approximately 1.5-fold higher in sows inseminated on day 1 in the pH 6.2 than in the pH 7.2 group. Furthermore, although there was no significant difference in the female-to-male ratio, the percentage of female piglets born was slightly higher in the pH 6.2 group than in the pH 7.2 group on day 2.

Conclusions

The method optimised in our study is simple, economical, and may enhance the number of female births without any decline in spermatozoa fertility.

Reproductive technologies in swine

This chapter highlights the importance of reproductive technologies that are applied to porcine breeds. Nowadays the porcine industry, part of a high technological and specialized sector, offers high-quality protein food. The development of the swine industry is founded in the development of breeding/genetics, nutrition, animal husbandry, and animal health. The implementation of reproductive technologies in swine has conducted to levels of productivity never reached before. In addition, the pig is becoming an important species for biomedicine. The generation of pig models for human disease, xenotransplantation, or production of therapeutic proteins for human medicine has in fact generated a growing field of interest.

Application of preserved boar semen for artificial insemination: Past, present and future challenges

Artificial insemination (AI) is now used for breeding more than 90% of the sows in most of the world's primary pork producing countries. Despite the advancement of methods to cryopreserve boar semen, frozen semen has not been routinely used on farms because of limited efficiency. Liquid semen on the other hand, with 1.5-3 billion sperm per dose preserved up to seven days in long-term extenders, is in common use and is largely responsible for the widespread use of AI. Breeding organizations have defined individual thresholds for useable semen at 60-80% for motility and bacterial load of 0-1000 CFU/mL. Improvement in preservation techniques for liquid semen and better education of producers has been responsible for the higher efficiency of pig breeding, as measured by conception rate and increased litter size, with a minimum number of sperm. The introduction of deep intrauterine AI and advances in breeding management have also been contributing factors. The present article reviews the worldwide application of preserved boar semen from past to present and delineates future challenges. Pathways to increase breeding efficiency are outlined. The reconciliation of AI with sustainable breeding strategies is increasingly important. In this sense, guidelines for the prudent use of antibiotics in semen extenders are proposed. More efficient and sustainable pig AI awaits the introduction of sex-sorted sperm into AI practice. Another critical milestone that needs to be achieved is the replacement of conventional antibiotics in extenders.

Effect of sex-sorting and cryopreservation on the post-thaw sperm quality of Iberian red deer spermatozoa

This study investigated the effect of sex-sorting and cryopreservation on post-thaw characteristics and fertility of red deer (Cervus elaphus) sperm for the first time. Semen was collected by electroejaculation from 10 mature stags during the breeding season, and each ejaculate split into four experimental groups: Bulk sorted spermatozoa, sorted but not sexed (BSS); sorted high purity X-spermatozoa (XSS); sorted high purity Y-spermatozoa (YSS); and, control non-sorted spermatozoa (NS). Following, all samples were frozen over liquid nitrogen. Two straws per stag and sample type were analyzed immediately post-thaw and following a 2-h incubation period at 37 °C. Post-thaw total motility (TM) as assessed by CASA was not different (P < 0.05) among NS, BSS and YSS sperm. For XSS, post-thaw TM was lower (39%, P < 0.05) than that for NS (54%) or BSS (50%), but similar (P > 0.05) to that of YSS (47%) sperm. The percentage of apoptotic spermatozoa as assessed by PI/YO-PRO-1 and flow cytometry analysis, was higher (17%, P ≤ 0.05) for XSS sperm than NS (12%), BSS (13%) and YSS (14%) sperm. Following incubation there were no differences (P > 0.05) in TM or percent apoptosis among treatments. Post-thaw chromatin stability calculated as the DNA fragmentation index (%DFI) was similar among treatments; following incubation %DFI increased in all except YSS, which displayed the lowest value (P < 0.05). Artificial insemination of synchronized hinds yielded 44, 52 and 62% delivery rates for YSS, NS and standard frozen-thawed sperm, respectively (P < 0.05). Notably, 93 and 55% of fawns born were males for the YSS and NS spermatozoa, respectively (P < 0.05). In summary, Y-sorted sperm displayed acceptable post-thaw sperm evaluation parameters and the expected offspring sex ratio. More studies are needed to understand the source of sperm damage that may compromise the fertility of Y-sorted red deer sperm.

Flow cytometric and near-infrared Raman spectroscopic investigation of quality in stained, sorted, and frozen-thawed buffalo sperm

Flow cytometry and Laser Tweezers Raman spectroscopy have been used to investigate Nili-Ravi buffalo (Bubalus bubalis) sperm from different samples (fresh, stained, sorted and frozen-thawed) of the flow-sorting process to optimize sperm sex sorting procedures. During the sorting and freezing-thawing processes, the two detection methods both indicated there were differences in mitochondrial activity and membrane integrity. Moreover, a dispersive-type NIR (Near Infrared Reflection) use of the Raman system resulted in the ability to detect a variety of sperm components, including relative DNA, lipid, carbohydrates and protein contents. The use of the Raman system allowed for PCA (principal components analysis) and DFA (discriminant function analysis) of fresh, stained, sorted and frozen-thawed sperm. The methodology, therefore, allows for distinguishing sperm from different samples (fresh, stained, sorted and frozen-thawed), and demonstrated the great discriminative power of ANN (artificial neural network) classification models for the differentiating sperm from different phases of the flow-sorting process. In conclusion, the damage induced by sperm sorting and freezing-thawing procedures can be quantified, and in the present research it is demonstrated that Raman spectroscopy is a valuable technology for assessing sperm quality.

Storage of sexed boar spermatozoa: Limits and perspectives

Despite the great potential application of sex-sorted spermatozoa in swine, the technology is not practiced in the pig industry because of technical factors and species-specific issues. The susceptibility of boar spermatozoa to stresses induced by the sorting procedure, the relative slowness of the sex-sorting process together with the high sperm numbers required for routine artificial insemination in pig are some of the main factors limiting the commercial application of this technology in pigs. This review briefly describes the damage to spermatozoa during sex sorting, focusing on an additional limiting factor: increased susceptibility of sexed boar spermatozoa to injuries induced by liquid storage and cryopreservation that, in turn, impairs sperm quality leading to unsatisfactory results in vivo. Strategies to extend the lifespan of sex-sorted boar spermatozoa and to improve their fertilizing ability after liquid storage or cryopreservation need to be implemented before this technology can be used in pig farms. In this regard, encapsulation in barium alginate membranes could be a promising technique to optimize the in vivo use of sexed boar spermatozoa, by protecting, targeting, and controlling the release of sperm into the female genital tract.

Sex selection of sperm in farm animals: status report and developmental prospects

Pre-selection of spermatozoa based on the relative DNA difference between X- and Y-chromosome bearing populations by flow cytometry is an established method that has been introduced into commercial cattle production. Although several important improvements have increased the sort efficiency, the fertilising ability of sexed spermatozoa based on offspring per insemination is still behind farmers' expectations. The main stress factors, especially on mitochondria, that reduce the lifespan of spermatozoa are described, and new technical as well as biological solutions to maintain the natural sperm integrity and to increase the sorting efficiency are discussed. Among these methods are the identification of Y-chromosome bearing spermatozoa by bi-functionalised gold nanoparticles and triplex hybridisationin vivoas well as new laser-controlled deflection system that replaces the deflection of spermatozoa in the electrostatic field. Additionally, as well as a new nonsurgical transfer system of spermatozoa into the oviduct of cows has been developed and allows a significant reduction of spermatozoa per transfer. Altogether, the improvements made in the recent years will allow a broader use of sex-sorted spermatozoa even in those species that require more cells than cows and sheep.

Improving the efficiency of insemination with sex-sorted spermatozoa

The sorting of X- and Y-chromosome-bearing spermatozoa by flow cytometry is nowadays one of the most apt assisted-reproduction technologies in livestock production. Potential economic and biological benefits, as well as those related to easier management of herds, have been reported arising out of the application of this technique, especially in cattle. Yet, the sex-sorting procedure induces damage to spermatozoa, affecting their function and fertilizing ability. Different species present varying degrees of susceptibility to damage from the sorting process and each has its own requirements for sex-sorted insemination procedures. Thus, several new protocols and strategies have been designed for the handling of sorted spermatozoa, with the main objective of optimizing their fertilizing ability and the consequent application of flow-cytometric sex-sorting technology. This article reviews current advances in this technology, pointing out the components to be improved before this technology may be widely applied in different domestic species.

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.

Early pregnancy loss in sows after low dose, deep uterine artificial insemination with sex-sorted, frozen–thawed sperm

Recent developments in reproductive technologies have enabled the production of piglets of a predetermined sex via non-surgical, low dose artificial insemination. The practical application of sex-sorting technology to the pig is made challenging by the large numbers of sperm required for successful insemination of sows. One way of overcoming the time required for sex-sorting may be to create a bank of cryopreserved, sex-sorted sperm, thus making available appropriate doses as sows require insemination. To date, little success has been achieved with non-surgical inseminations of sex-sorted boar sperm. This study attempted to achieve litters of a predetermined sex after a double insemination of sows with 160x10(6) sex-sorted, frozen-thawed sperm. Sows were synchronised and sperm were non-surgically inseminated into the proximal third of the uterine horn at 36 and 42 h after hCG administration. Sows inseminated with sex-sorted sperm achieved similar pregnancy rates to those receiving an equal dose of unsorted, frozen-thawed sperm. However, all sows conceiving after insemination with sex-sorted sperm returned to oestrus within 57 days of insemination. This was a higher rate of pregnancy loss than observed for sows inseminated with unsorted sperm (37.5%; P=0.031). A combination of low sperm numbers and potentially compromised developmental capability of embryos derived from sex-sorted sperm may have resulted in this early stage loss of pregnancy.

Artificial insemination in the anoestrous and the postpartum white rhinoceros using GnRH analogue to induce ovulation

The objective of this study was to develop AI and to achieve first time pregnancy in a nulliparous rhinoceros. For this, one 24-year-old irregular cycling female white rhinoceros was selected, which had never been mated. The endocrine function was monitored by faecal and serum pregnane analysis. Ultrasound determined the optimal day for AI by measuring follicle sizes of 2.0, 2.6, 3.0, 3.2 cm on days -6, -4, -1, 0 of the induced oestrous cycle, respectively. AI was performed and ovulation induced when a pre-ovulatory-sized follicle was present using GnRH analogue, deslorelin. Fresh semen was deposited in the uterine horn using a patented AI catheter overcoming the hymeneal membrane and torturous cervical folds non-surgically. Moreover, ultrasound monitoring of the uterine involution and ovarian activity on days 16, 26, 30 postpartum facilitated the induction of and the AI on the first postpartum oestrous in a rhinoceros using GnRH analogue. Two consecutive pregnancies were achieved by AI for the first time in the rhinoceros. Pregnancies were diagnosed by elevated serum and faecal 20-oxo-pregnane concentrations. In addition ultrasound measured biometric parameters of the two foetuses on days 86 and 133 of gestation. Two female calves were born after 490 and 502 days of gestation, yet one calf was stillborn. AI in rhinoceros might now be used as assisted reproduction technology tool to boost critically small captive rhinoceros populations.

Insemination with sex sorted fresh bovine spermatozoa processed in the presence of antioxidative substances

Flow cytometrically sex sorted spermatozoa are reduced in their fertilizing capacity, particularly when stored either in cooling extender or after freezing in liquid nitrogen. So far, preservation methods for sorted spermatozoa have differed only marginally from procedures used for unsorted semen. In the present study, a TRIS extender was modified to balance major cell damage caused by the sorting process and by liquid storage of the sorted spermatozoa. The new extender, containing a combination of antioxidants (AO) and bovine serum albumin (BSA), significantly increased the lifespan and fertilizing capacity of sex sorted spermatozoa. No significant differences were observed between unsorted controls and sorted samples for motility and status of sperm membranes as tested by fluorescein-isothiocyanat-peanut agglutinin/propidium iodide (FITC-PNA/PI). Acrosome integrity of spermatozoa was significantly better when semen was stored at 15 degrees C for 24 and 48 h in an extender containing AO with or without BSA as compared with controls (p < 0.05). There were no significant differences, in pregnancy rates of heifers inseminated at a natural oestrus, between unsorted controls (16/24, 66.7%) and both sorted groups (AO + BSA: 18/31, 58.1% and AO-BSA: 12/22, 54.5%). Additionally, it was shown for the first time that artificial insemination (AI) with liquid sexed bull spermatozoa stored for 72 h after sorting can result in pregnancy rates similar to AI with non-sorted semen.

Sex Preselection in Bovine by Separation of X- and Y-Chromosome Bearing Spermatozoa

Flow cytometrically-sorted sperm has been involved in the production of sex preselected offspring. More than 30,000 bovine offspring have been produced using AI and other means using spermatozoa separated by flow cytometer. Flow cytometric sperm sorting based on differences in their DNA content is the best method for separation of X- and Y-chromosome bearing spermatozoa. At first, flow cytometers were modified for DNA confirmation and sorting of sperm with high resolution. The beveled insertion needle can regulate orientation of flat-shaped bull sperm heads. The forward fluorescence detector is essential for measuring the DNA content of sperm. Recently, high-speed sperm sorting with orienting nozzles has resulted in production of 90% pure X- and Y-sperm at rate of 15-20 million sperm per hour. Application of this new technique will enable conduct of more conventional technologies for both artificial insemination and cryopreservation in the bovine and in other farm animals using X- or Y-sperm.

Challenges in Pig Artificial Insemination

Semen extended in a liquid state, together with conventional artificial insemination (AI), is the sole sperm technology used by the pig industry. Sperm technologies known for many years, such as cryopreservation, and others developed during recent years, such as sperm sexing, have not yet been integrated into commercial use. Moreover, there has recently been an explosion of new technologies, such as sperm mediated gene transfer or encapsulated spermatozoa which need additional supportive techniques before they can be economically applied to pig breeding. The speed with which the aforementioned sperm technologies are accepted and utilized by the pig industry depends on the availability of efficient insemination procedures. Therefore, AI is entering a new dimension where it will be converted into a tool for the efficient application of current and new sperm technologies. Some new insemination procedures have been recently developed. This review examines the suitability of available insemination procedures for the efficient application of current, emergent and future sperm technology to the pig industry.

Low dose insemination in cattle with the Ghent device

A new artificial insemination device for semen deposition near the uterotubal junction (UTJ) in cattle (Ghent device) was developed at Ghent University (Belgium). In this study, UTJ insemination of dairy cows with the Ghent device was compared with the conventional insemination technique to evaluate the effect on pregnancy rates after insemination with different doses of semen. In each of three field trials, the cows (n=795, 659, 360) and heifers (n=253, 182, 231) were randomly assigned to receive 12 million sperm deposited in the uterine body using conventional techniques (control) or a reduced sperm dose (RSD) deposited in the same manner as the control or bilateral deposition near the uterotubal junction using the Ghent device (Ghent). Sperm dosages for RSD and Ghent inseminations were 8, 4, and 2 million sperm for field trials 1-3, respectively. In the multivariable analysis, the pregnancy rates were significantly affected by the parity of the cow (p</=0.008) in each of the three trials, by the sire (p=0.014, 0.009) in trials 1 and 3, and by the inseminator (p<0.001) in trial 2. In none of the trials were the pregnancy rates significantly affected by the insemination technique, the order of insemination (first, second, or third), the breed of the bull or the dosage sensitivity of the bull. In conclusion, neither sperm dosage nor site of semen deposition influenced pregnancy rates in the present study.

Flow cytometric sexing of mammalian sperm

This review reexamines parameters needed for optimization of flow cytometric sexing mammalian sperm and updates the current status of sperm sexing for various species where this technology is currently being applied. Differences in DNA content have provided both a method to differentiate between these sex-determining gametes and a method to sort them that can be used for predetermining sex in mammals. Although the DNA content of all cells for each mammalian species is highly conserved, slight but measurable DNA content differences of sperm occur within species even among cattle breeds due to different sizes of Y-chromosomes. Most mammals produce flattened, oval-headed sperm that can be oriented within a sorter using hydrodynamic forces. Multiplying the percentage the difference in DNA content of the X- or Y-chromosome bearing sperm times the area of the flat profile of the sperm head gives a simple sorting index that suggests that bull and boar sperm are well suited for separation in a flow sorter. Successful sperm sexing of various species must take into account the relative susceptibilities of gametes to the stresses that occur during sexing. Sorting conditions must be optimized for each species to achieve acceptable sperm sexing efficiency, usually at 90% accuracy. In the commercial application of sperm sexing to cattle, fertility of sex-sorted bull sperm at 2 x 10(6)/dose remains at 70-80% of unsexed sperm at normal doses of 10 to 20 x 10(6) sperm. DNA content measurements have been used to identify the sex-chromosome bearing sperm populations with good accuracy in semen from at least 23 mammalian species, and normal-appearing offspring have been produced from sexed sperm of at least seven species.

Incidence of Unilateral Fertilizations after Low Dose Deep Intrauterine Insemination in Spontaneously Ovulating Sows under Field Conditions

A new procedure for non-surgical deep intrauterine insemination (DUI) in unrestrained sows hormonally induced to ovulate, has been reported. In comparison with standard artificial insemination (AI), with this procedure, the sperm numbers inseminated can be reduced 20-fold without reducing the reproductive performance of these hormonally treated sows. The present study evaluated, using two experiments, the reproductive performance applying 20-fold different sperm numbers per AI dose using DUI or standard AI in spontaneously ovulating sows, under field conditions. In experiment 1, AI was applied to crossbred sows at 12, 24 and 36 h after onset of spontaneous oestrus using one of the following two regimes: (i) DUI (treatment) with 0.15 x 10(9) fresh boar spermatozoa in 5 ml of Beltsville thawing solution (BTS) extender (n = 95), and (ii) standard cervical AI (control) with 2.85 x 10(9) fresh spermatozoa in 95 ml of BTS extender (n = 95). The farrowing rates of the two groups of sows were statistically similar (NS). However, a decrease (p < 0.002) in litter size and the total number of pigs born alive was observed in sows inseminated with the DUI procedure. In experiment 2, 42 post-weaned oestrus sows were inseminated following the same design described for experiment 1 during spontaneous oestrus. On day 6 after onset of oestrus, the proximal segment of the uterine horns of the sows were flushed under surgery to retrieve eventual embryos and evaluate the success of fertilization per cornua (e.g. occurrence of effective uni- vs bilateral sperm transport rendering uni- or bilateral, complete or partial fertilization). Retrieved embryos were assessed for cleavage and number of accessory spermatozoa. Although identical overall pregnancy rates were achieved in both insemination groups, the percentage of sows with partial bilateral fertilization and unilateral fertilization was markedly higher (p < 0.05) in the DUI group (35%) compared with the control (standard AI) group (5%), with a consequent lower (p < 0.001) percentage of viable early embryos after DUI. The number of accessory spermatozoa in the zona pellucida of the embryos was highly variable, but higher (p < 0.001) in control animals than in DUI-AI. No accessory spermatozoa were found in oocytes retrieved from sows depicting unilateral fertilization. In conclusion, DUI in spontaneously ovulating sows with 0.15 x 10(9) spermatozoa renders similar farrowing rates but a lower litter size compared with use of standard AI with a 20-fold higher sperm dose. The lower litter size ought to be related to a decreased distribution of spermatozoa after DUI leading to a higher incidence of partial bilateral and unilateral fertilization.

An update on Reproductive Technologies with Potential Short-Term Application in Pig Production

Over the past decade, there has been an increase in the development and/or in the improvement of emerging reproductive technologies in pigs. Among emerging reproductive technologies with potential short-term application in pig production are: artificial insemination with low number of spermatozoa, cryopreservation of spermatozoa and embryos, sperm sexing, and non-surgical embryo transfer. The following review will give emphasis to recent advancements in these reproductive technologies that are starting to show possibilities of serious applications under field conditions.

Effect of staining and sorting on boar sperm membrane integrity, mitochondrial activity and in vitro blastocyst development

The objective of this study was to determine the effects of staining with Hoechst 33342 and of the entire sorting procedure on boar sperm membrane integrity (using Annexin-V/PI), mitochondrial activity (using JC-1/SYBR/PI) and blastocyst development in vitro; the effect of storage at 17 degrees C for 24h prior to Hoechst staining and sorting was also investigated. The Hoechst staining and the whole sorting procedure reduced the percent of live spermatozoa in both fresh (day 0) and stored (day 1) semen, as determined by both assays; nevertheless, there was no increase in live sperm cells showing signs of early damage (Annexin-V positive, propidium negative), whose percentages remained nearly zero. The majority of Annexin-V positive cells were propidium positive, therefore dead. JC-1 staining evidenced a correlation between mitochondrial activity and viability. However, a significant difference between viable sperm cells and sperm cells with active mitochondria was detected in control and stained sperm, whereas almost all viable sorted spermatozoa had active mitochondria. No significant differences in the in vitro produced blastocysts both on day 0 and 1 were observed. In conclusion, despite the damages induced by sorting procedures, semen sorted as fresh or after storage at 17 degrees C can be successfully used for in vitro production of pig embryos.

Influence of storage time on functional capacity of flow cytometrically sex-sorted boar spermatozoa

Sex-sorting of boar spermatozoa is an emerging biotechnology, still considered suboptimal owing to the slowness of the process, which requires long sorting periods to obtain an adequate number of spermatozoa to perform a non-surgical insemination. This period involves storage of sorted cells that could impair their functional capacity. Here, we have studied how the storage of sex-sorted boar spermatozoa affects their functional capacity. Sorted spermatozoa were assessed at various times (0, 2, 5h or 10h) during storage after sorting and compared with diluted and unsorted spermatozoa for sperm motility patterns, plasma membrane and acrosomal integrity and their ability to penetrate homologous IVM oocytes. Sex-sorted sperm motility and membrane integrity only decreased significantly (p<0.05) by the end of the storage period (10h) compared to unsorted spermatozoa. Sperm velocity, ALH and Dance increased significantly (p<0.05), immediately post-sorting, returning to unsorted sperm values during storage. Acrosome integrity was not seriously affected by the sorting process, but decreased (p<0.05) during storage after sorting. Sorted spermatozoa stored 2h after sorting did not differ from unsorted in penetration rates and numbers of spermatozoa per oocyte, reaching the highest (p<0.05) penetration rates and sperm numbers per oocyte, when co-cultured for 6 or more hours. Non-storage or storage for 5h or 10h negatively (p<0.05) affected sperm penetration ability. In conclusion, although flow cytometrically sex-sorted spermatozoa are able to maintain motility, viability and acrosomal integrity at optimal levels until 10h of storage after sorting, fertilizing ability is maintained only over shorter storage times (<5h).

Perspectives for artificial insemination and genomics to improve global swine populations

Civilizations throughout the world continue to depend on pig meat as an important food source. Approximately 40% of the red meat consumed annually worldwide (94 million metric tons) is pig meat. Pig numbers (940 million) and consumption have increased consistent with the increasing world population (FAO 2002). In the past 50 years, research guided genetic selection and nutrition programs have had a major impact on improving carcass composition and efficiency of production in swine. The use of artificial insemination (AI) in Europe has also had a major impact on pig improvement in the past 35 years and more recently in the USA. Several scientific advances in gamete physiology and/or manipulation have been successfully utilized while others are just beginning to be applied at the production level. Semen extenders that permit the use of fresh semen for more than 5 days post-collection are largely responsible for the success of AI in pigs worldwide. Transfer of the best genetics has been enabled by use of AI with fresh semen, and to some extent, by use of AI with frozen semen over the past 25 years. Sexed semen, now a reality, has the potential for increasing the rate of genetic progress in AI programs when used in conjunction with newly developed low sperm number insemination technology. Embryo cryopreservation provides opportunities for international transport of maternal germplasm worldwide; non-surgical transfer of viable embryos in practice is nearing reality. While production of transgenic animals has been successful, the low level of efficiency in producing these animals and lack of information on multigene interactions limit the use of the technology in applied production systems. Technologies based on research in functional genomics, proteomics and cloning have significant potential, but considerable research effort will be required before they can be utilized for AI in pig production. In the past 15 years, there has been a coordinated worldwide scientific effort to develop the genetic linkage map of the pig with the goal of identifying pigs with genetic alleles that result in improved growth rate, carcass quality, and reproductive performance. Molecular genetic tests have been developed to select pigs with improved traits such as removal of the porcine stress (RYR1) syndrome, and selection for specific estrogen receptor (ESR) alleles. Less progress has been made in developing routine tests related to diseases. Major research in genomics is being pursued to improve the efficiency of selection for healthier pigs with disease resistance properties. The sequencing of the genome of the pig to identify new genes and unique regulatory elements holds great promise to provide new information that can be used in pig production. AI, in vitro embryo production and embryo transfer will be the preferred means of implementing these new technologies to enhance efficiency of pig production in the future.

First Established Pregnancies in Mediterranean Italian Buffaloes (Bubalus bubalis) Following Deposition of Sexed Spermatozoa near the Utero Tubal Junction

At the time of AI following Ovsynch protocol, a total of 51 buffaloes were randomly divided in a first group (n = 30) subjected to conventional AI into the uterine body with 20 million non-sex sorted frozen-thawed spermatozoa, while a second group (n = 21) was inseminated near the utero-tubal junction (UTJ) ipsilateral to the ovary carrying the preovulatory follicle with 2.5 million live (4 million total) sex-sorted frozen-thawed spermatozoa. The semen used for flowcytometric sorting was collected and processed on a farm in Italy, and then shipped to a laboratory in Germany. Eleven buffaloes were inseminated with X-chromosome bearing spermatozoa and 10 with Y-chromosome bearing spermatozoa. Conception rates after conventional and UTJ inseminations were 43.3% (n = 13) and 42.8% (n = 9) respectively (p = 0.97). Eight of the nine foetuses obtained after insemination with sexed spermatozoa corresponded to the sex as predicted by the cell sorting procedure (five male and four female foetuses by ultrasound vs six male and three female foetuses by cell sorting). In conclusion, for the first time buffalo semen has been successfully subjected to procedures for flowcytometric sperm sorting and freezing. Low doses of sexed spermatozoa have been deposited near the UTJ giving conception rates similar to those of conventional AI with full dose.

Preselection of sex of offspring in swine for production: current status of the process and its application

It is estimated that as many as 30,000 offspring, mostly cattle, have been produced in the past 5 years using AI or some other means of transport with spermatozoa sexed by flow cytometric sperm sorting and DNA as the marker of differentiation. It is well documented that the only marker in sperm that can be effectively used for the separation of X- and Y-chromosome bearing spermatozoa is DNA. The method, as it is currently used worldwide, is commonly known as the Beltsville Sperm Sexing Technology. The method is based on the separation of sperm using flow cytometric sorting to sort fluorescently (Hoechst 33342) labeled sperm based on their relative content of DNA within each population of X- and Y-spermatozoa. Currently, sperm can be produced routinely at a rate of 15 million X- and an equal number of Y-sperm per hour. The technology is being applied in livestock, laboratory animals, and zoo animals; and in humans with a success rate of 90-95% in shifting the sex ratio of offspring. Delivery of sexed sperm to the site of fertilization varies with species. Conventional AI, intrauterine insemination, intra-tubal insemination, IVF with embryo transfer and deep intrauterine insemination are effectively used to obtain pregnancies dependent on species. Although sperm of all species can be sorted with high purity, achieving pregnancies with the low numbers of sperm needed for commercial application remains particularly elusive in swine. Deep intrauterine insemination with 50-100 million sexed boar sperm per AI has given encouragement to the view that insemination with one-fiftieth of the standard insemination number will be sufficient to achieve pregnancies with sexed sperm when specialized catheters are used. Catheter design, volume of inseminate, number of sexed sperm are areas where further development is needed before routine inseminations with sexed sperm can be conducted in swine. Cryopreservation of sex-sorted sperm has been routinely applied in cattle. Although piglets have been born from frozen sex-sorted boar sperm, freezing and processing protocols in combination with sex-sorted sperm are not yet optimal for routine use. This review will discuss the most recent results and advances in sex-sorting swine sperm with emphasis on what developments must take place for the sexing technology to be applied in commercial practice.

Improving the efficiency of sperm technologies in pigs: the value of deep intrauterine insemination

The use of AI in pigs has dramatically expanded in the last few years. New methodological advances in AI are required to serve the requirements of new sperm technologies, such as the use of low dose AI, because the use of cervical AI has a very low efficiency leading to low fertility results. One of the strategies devised to meet these requirements is the deposition of semen near the site of fertilization in the oviduct. Using deep intrauterine insemination with a specially designed catheter, a 20-fold reduction in the number of freshly and diluted inseminated spermatozoa can be achieved without decreasing farrowing rates. Moreover, an advantage of deep intrauterine insemination is the possibility of using processed, 'weaker' spermatozoa such as those that have been frozen-thawed or sex-sorted. Although deep intrauterine insemination should be of benefit to the pig industry, more investigations are needed to understand the mechanisms related to sperm colonization of the oviducts and identify the minimal sperm numbers needed to obtain maximal fertility results for processed and unprocessed boar spermatozoa.

Production of piglets with sexed semen employing a non-surgical insemination technique

The aim of the present study was to ascertain whether multiparous sows could successfully be inseminated with sexed semen non-surgically. Spermatozoa were stained with Hoechst 33342 and separated flowcytometrically in X- and Y-chromosome bearing sperm populations employing the Beltsville Sperm Sexing Technology (BSST). After weaning, estrus was induced in sows with PMSG and hCG. Animals were inseminated once per estrus non-surgically with a specially designed catheter into the tip of the uterine horn, employing 50x10(6) of either sexed or non-sexed spermatozoa diluted in 2 ml Androhep. Pregnant sows were allowed to go to term. Mean pregnancy rate from inseminations with unsexed spermatozoa was 54.5% whereas inseminations with sexed spermatozoa resulted in 33.3% pregnant sows. All but one piglet born after insemination with sexed semen were of the predicted sex. The sex of those piglets born after inseminations with non-sexed spermatozoa was 61.1% for male and 38.9% for female sex. It is concluded that non-surgically inseminations with flowcytometrically sexed spermatozoa can be conducted successfully.

Advanced assisted reproduction technologies (ART) in goats

Assisted reproduction technologies (ART) are reviewed with special emphasis on goat genetic improvement programs. Estrous synchronization and artificial insemination are the most commonly used ART worldwide because of their simplicity and excellent cost/benefit, especially when proven sires are used. Multiple ovulation and embryo transfer (MOET) has not become widely used due to its unpredictability. In vitro embryo production using oocytes collected by laparoscopy from valuable donors has the potential to improve the results obtained from MOET and expand its applications (for example, using prepubertal donors). However, the costs and inefficiencies of the system might restrict its use to special situations. Finally, transgenesis and cloning are expected to have a significant impact on the future genetic improvement of livestock. However, because of low efficiencies and high costs, their present use is restricted to applications with high returns such as the production of recombinant proteins of pharmaceutical and biomedical interest.

Integration of sperm sexing technology into the ART toolbox

Sex-sorting of mammalian spermatozoa has applications for genetic improvement of farm animals, in humans for the control of sex-linked disease, and in wildlife as a captive management strategy and for the re-population of endangered species. Considerable research has been undertaken worldwide on the Beltsville sperm sexing technology, the only effective method for pre-selection of sex of offspring. The combination of this method with assisted reproductive technologies has resulted in the birth of offspring in a wide range of animals, including cattle, the only livestock species in which sperm sexing is used commercially. Major improvements in the efficiency of sorting, in particular the development of high speed sorting (15 million X and Y spermatozoa per hour) have led to the production of offspring using conventional and low dose AI and the successful cryopreservation of sorted spermatozoa in cattle, sheep, horses and elk. A major limitation remains the short viable lifespan of sorted spermatozoa in the female genital tract, in most species necessitating sperm deposition deep in the uterus, and close to the expected time of ovulation, for acceptable fertility after in vivo insemination. Special deep uterine insemination technology has been employed to produce offspring in pigs and horses using low sperm doses. Considerable attention has been paid to reduction of the damage and capacitation-like changes to spermatozoa that result from flow cytometric sorting and from freezing and thawing. However, high-purity sorting of liquid-stored or frozen-thawed spermatozoa for immediate use, or re-cryopreservation for later use, does not reduce its fertilizing capacity in vitro, allowing its combination with in vitro fertilization or juvenile in vitro embryo transfer to produce blastocysts, and offspring in sheep and cattle after embryo transfer. Further research into sorting and preservation methods that incorporate strategies to prevent destabilization of sperm membranes may improve the fertilizing lifespan of flow cytometrically sorted spermatozoa. With continued improvement in sorting instrumentation and biological handling, sorting efficiency should reach a point where commercially acceptable pregnancy rates may be achieved in a number of species after conventional or deep uterine insemination.

Intra-uterine Insemination in Farm Animals and Humans

Artificial insemination (AI) is the oldest and currently most common technique in the assisted reproduction of animals and humans. The introduction of AI in farm animals was forced by sanitary reasons and the first large-scale applications with a commercial goal were performed in cattle in the late 1930s of last century. After the Second World War, cryopreservation of semen facilitated distribution and AI was mainly performed for economic reasons, especially in dairy cattle industry. In humans however, AI was initially performed in cases of physiological and psychological sexual dysfunction, but later on also in cases of infertility caused by immunological problems. Currently, the most common indications for intra-uterine insemination (IUI) in humans are unexplained infertility and male subfertility. In these cases, IUI is considered as the treatment of the first choice, before more invasive techniques such as in vitro fertilization (IVF) and intracytoplasmatic sperm injection (ICSI) are used. In contrast with humans, the quantity and quality of semen produced by farm animals is much higher and permits dilution and production of several insemination doses per ejaculate. However, with the introduction of sex-sorted semen in farm animals, the same problem of low-quality semen as in humans has arisen. In cattle, pigs and horses, conventional insemination with low numbers of sex-sorted spermatozoa results in a significant decrease in fertility. To improve the fertility rates with this semen, new insemination techniques have been developed in order to deposit spermatozoa closer to the site of fertilization. In sows and mares the advantage of utero-tubal junction (UTJ) insemination has already been proven; however, in cattle it is still under investigation. In this review, the differences and similarities in the application of AI between animals and humans are discussed and as AI in farm animals is most successful in cattle, the situation in this species is elaborated the most.

Preservation and artificial insemination of sexed semen in sheep

Sperm-sexing technology using flow cytometry is in advanced stages of development for the sperm of several species. The sorting process could compromise sperm viability and sperm require specific handling procedures both before and after sorting to maintain the integrity and function of the sorted sperm. Standard freezing protocols have been modified for post-sorting cryopreservation of sperm and frozen sperm have been successfully thawed, sorted, refrozen and subsequently used to produce offspring. The relatively low numbers of available sorted sperm have, in some cases, led to modification of artificial insemination techniques to maximise efficiency of use. Multiple ovulation and embryo transfer, or in vitro fertilisation and associated technology, may lead to the more efficient use of sexed sperm.