New developments in low-dose insemination technology

Combining Fixed-Time Insemination and Improved Catheter Design in an Effort to Improve Swine Reproduction Efficiency

Conventional practice is to breed sows by artificial insemination (AI) at least twice using approximately three billion sperm per insemination upon estrus at standing heat. This research explored the use of combined technologies, including fixed-time insemination (FTAI) and an alternative catheter design that reportedly reduces semen backflow, in order to reduce the number of inseminations and the semen dosage and maintain reproductive efficiency. The FTAI technique used in this study was to inject I.M. 600 IU equine chorionic gonadotropin (eCG) at weaning and 5 mg porcine luteinizing hormone (pLH) to stimulate ovulation 80 h later, followed by a single insemination 36 h after the pLH injection. The two catheters used in this study were a conventional foam-tipped insemination catheter and a Gedis catheter. The Gedis catheter is designed to be completely inserted into the vagina. The semen is enclosed along the length of the rod and held in place by a gel cap that melts when inserted into the cervix. Sows were assigned to the following treatments: Group 1 (n = 135), bred twice with a conventional catheter and a standard semen dose of approximately three billion sperm in 80 mL; Group 2 (n = 123), FTAI with conventional catheter and a standard semen dose; Group 3 (n = 127), FTAI with Gedis catheter and a standard semen dose; Group 4 (n = 126), FTAI with Gedis catheter and a reduced semen dose with one billion sperm. The farrowing rates were 81.6%, 77.7%, 74.0%, and 62.7% for Groups 1 to 4, respectively. The likelihood of farrowing was lower for Group 3 and Group 4 compared to Group 1 (odds ratio (OR) = 0.57; p = 0.08 and OR = 0.35; p = 0.001, respectively). Likewise, litter size of Group 3 and Group 4 was smaller than Group 1 (p = 0.006 and p = 0.04, respectively). Overall, the combination of Gedis catheter and FTAI resulted in decreased reproductive performance that outweighed the value of using less semen.

A new device for deep cervical artificial insemination in gilts reduces the number of sperm per dose without impairing final reproductive performance

Background

The aim of this study was to evaluate the reproductive performance of a new artificial insemination (AI) device specifically designed for gilts (Deep cervical AI, Dp-CAI) by means of which the sperm is deposited deeply in the cervix (8 cm more cranial than in traditional cervical insemination-CAI). New AI techniques have arisen in recent decades in the porcine industry, such as post-cervical artificial insemination (PCAI), which involves depositing the sperm in the body of the uterus [through a catheter (outer tube)-cannula (inner tube)] rather than by CAI. Although the PCAI method has been successfully applied in farm conditions to reduce sperm doses without impairing the reproductive performance, this technique has limitations in gilts mainly because of the difficulty involved in introducing the inner cannula through the cranial part of the cervix. For this reason, the Dp-CAI method described herein may be considered as an alternative to CAI and PCAI methods in gilts.

Results

Gilts were divided in two experimental groups: 1) Dp-CAI: gilts (n = 1166) inseminated using 1.5 × 10⁹ sperm/45 mL; 2) CAI (as a control group): gilts (n = 130) inseminated using 2.5 × 10⁹ sperm/85 mL. The Dp-CAI method was successfully applied in 88.90% of the gilts, with no differences detected between gilts with 1 or 2 previous oestrus cycles, although the catheter could be introduced more deeply in 2 oestrus gilts (P < 0.05). As the length of the insemination device that could not be introduced increased (at the moment of insemination), so the success rate of the Dp-CAI device fell, as did the total number of piglets born. When the reproductive output in CAI and Dp-CAI was compared, none of the parameters analysed [pregnancy and farrowing rates (%), and number of piglets born (total and live)] showed significant differences.

Conclusions

The use of the Dp-CAI technique provides a new AI method as an alternative to CAI and PCAI for pigs. The device, especially designed for gilts, was used with a high degree of success reducing conventional sperm doses without impairing reproductive parameters.

Electronic supplementary material

The online version of this article (10.1186/s40104-019-0313-1) contains supplementary material, which is available to authorized users.

Effect of numbers of sperm and timing of a single, post-cervical insemination on the fertility of weaned sows treated with OvuGel®

Variability in estrus and ovulation requires multiple inseminations during estrus to ensure one AI occurs close to ovulation. Induction of ovulation after weaning improves synchrony of ovulation and allows for fixed time AI. However, the interaction between number of sperm in the AI dose and the timing of insemination has not been fully investigated. The objective of this study was to determine the effects of sperm numbers used in a single post-cervical insemination (PCAI) and the timing of insemination following induced ovulation in weaned sows. The experiment was performed using sows (n = 641) allotted by parity (1-6) and lactation length (19.5 d) to receive a single PCAI using 1.5 or 2.5 billion motile sperm at either 22, 26, or 30 h following administration of a GnRH agonist, triptorelin acetate (OvuGel^®) at 96 h post-weaning. Sows received boar contact once daily 3-6 d following weaning. A sub-population of the sows (n = 499) were assessed for follicle size and ovulation utilizing ultrasound at 8 h intervals. There was no interaction of number of sperm and timing of insemination for any response measure (P > 0.10). Wean to estrus interval (4.8 d), duration of estrus (1.9 d), and expression of estrus (88.0%), were not different among treatments (P > 0.10). Of sows scanned by ultrasound at the time of OvuGel^®, 88.2% had large follicles, 10.9% had small, medium or cystic sized follicles, and 0.9% had corpora lutea. The proportion of sows that ovulated averaged 94%, and differed by time of AI (P ≤ 0.05) but not by number of sperm. Pregnancy rate and farrowing rate tended to be affected by dose (P ≤ 0.10), while time of insemination affected pregnancy rate and tended to influence farrowing rate (P ≤ 0.10). Farrowing rate was greater (P < 0.0001) with use of 2.5 than 1.5 billion sperm and insemination at 22 and 26 h compared to 30 h after OvuGel^® (P ≤ 0.10). Farrowing rate was also affected by parity, estrus expression, ovulation and ovarian abnormalities (P < 0.05). Of the 12% of weaned sows that did not exhibit estrus, approximately 50% farrowed a litter. Total born and born alive were affected by dose (P < 0.05) but not time of insemination with both measures increased with 2.5 compared to 1.5 billion sperm (P < 0.05). The results of this study indicate that induction of ovulation in weaned sows resulted in 88% of sows ovulating within a 24 h period. Fertility was improved with a single, fixed time AI using 2.5 compared to 1.5 billion motile sperm and insemination at 22-26 h after OvuGel^® compared to 30 h.

The Importance of the Periconception Period: Immediate Effects in Cattle Breeding and in Assisted Reproduction Such as Artificial Insemination and Embryo Transfer

In livestock breeding, the successful outcome is largely depending on the "periconception environment" which, in a narrow sense, refers to the genital tract, where gametogenesis and embryogenesis occur. During these early stages of development, gametes and embryos are known to be particularly sensitive to alterations in their microenvironment. However, as the microenvironment somehow reflects what is going on in the external world, we must widen our definition of "periconception environment" and refer to all events taking place around the time of conception, including metabolic state and health and nutrition of the dam. In modern dairy cows that have to manage an optimal reproductive performance with continued growth and high milk yield, the periconception period is particularly challenging. The metabolic priority for growth and lactation is known to generate adverse conditions hampering optimal ovarian function, oocyte maturation, and development of embryo/fetus. In addition, by using artificial reproductive technologies (ARTs), gametes and/or embryos of livestock are exposed to unnatural conditions outside the male and female genital tract. Artificial insemination, the most widely used technique, is currently yielding pregnancy rates similar to natural mating, and calves produced by AI are equally viable after natural mating. In contrast, other ART, such as multiple ovulation and embryo transfer, have been reported to induce changes in gene expression and DNA methylation patterns with potential consequences for development.Finally, the "periconceptional" environment has been shown to not only influence the successful establishment of pregnancy but also the long-term health and productivity of the offspring. Hence, the optimization of management around the time of conception might open doors to improve animal production and product quality.

Sex-Sorted Boar Sperm - An Update on Related Production Methods

As in other mammals, sex sorting of pig sperm is based on quantitative flow cytometry. A major disadvantage of the technique is the relatively low efficiency to produce enough sorted sperm for artificial insemination. However, several approaches are on the way to make sexed pig sperm available for commercial application. In this context, for example, the growing field of nanotechnology may significantly contribute to these developments, as it provides highly efficient bio-nanoprobes, for example, based on plasmonic nanoparticles. Independent of the method, further development requires enormous investments and set-up of logistics to get the technology into the practical pig market. Only global players will be able to establish the necessary research projects, but in the end, a significant shift of sex ratios will be available for pig producers as it is already the case for the dairy industry.

Efficient Boar Semen Production and Genetic Contribution: The Impact of Low-Dose Artificial Insemination on Fertility

Diluting semen from high fertile breeding boars, and by that inseminating many sows, is the core business for artificial insemination (AI) companies worldwide. Knowledge about fertility results is the reason by which an AI company can lower the concentration of a dose. Efficient use of AI boars with high genetic merit by decreasing the number of sperm cells per insemination dose is important to maximize dissemination of the genetic progress made in the breeding nucleus. However, a potential decrease in fertility performance in the field should be weighed against the added value of improved genetics and, in general, is not tolerated in commercial production. This overview provides some important aspects that influence the impact of low-dose AI on fertility: (i) the importance of monitoring field fertility, (ii) the need for accurate and precise semen assessment, (iii) the parameters that are taken into account, (iv) the application of information from genetic and genomic selection and (v) the optimization when using different AI techniques. Efficient semen production, processing and insemination in combination with increasing use of genetic and genomic applications result in maximum impact of genetic trend.

Artificial insemination in pigs today

Use of artificial insemination (AI) for breeding pigs has been instrumental for facilitating global improvements in fertility, genetics, labor, and herd health. The establishment of AI centers for management of boars and production of semen has allowed for selection of boars for fertility and sperm production using in vitro and in vivo measures. Today, boars can be managed for production of 20 to 40 traditional AI doses containing 2.5 to 3.0 billion motile sperm in 75 to 100 mL of extender or 40 to 60 doses with 1.5 to 2.0 billion sperm in similar or reduced volumes for use in cervical or intrauterine AI. Regardless of the sperm dose, in liquid form, extenders are designed to sustain sperm fertility for 3 to 7 days. On farm, AI is the predominant form for commercial sow breeding and relies on manual detection of estrus with sows receiving two cervical or two intrauterine inseminations of the traditional or low sperm doses on each day detected in standing estrus. New approaches for increasing rates of genetic improvement through use of AI are aimed at methods to continue to lower the number of sperm in an AI dose and reducing the number of inseminations through use of a single, fixed-time AI after ovulation induction. Both approaches allow greater selection pressure for economically important swine traits in the sires and help extend the genetic advantages through AI on to more production farms.

Migração espermática em suínos após inseminação artificial intrauterina profunda

A inseminação artificial intrauterina profunda (IIP) é de grande importância para a indústria suinícola, em função do maior número de doses produzidas por reprodutores de alto mérito genético e da possibilidade da utilização de biotecnologias, como sêmen sexado e/ou congelado. Entretanto, necessita-se compreender com maior propriedade os mecanismos pelos quais os espermatozoides colonizam as tubas uterinas. Assim sendo, pretende-se com o presente experimento avaliar a existência ou não de migração intraperitoneal de espermatozoides inseminados profundamente em um dos cornos uterinos, mediante a obtenção de oócitos fertilizados no corno contralateral à inseminação e seccionado na base, na junção com o corpo do útero. Quatorze fêmeas pluríparas foram divididas em dois grupos experimentais, sendo que em um deles as fêmeas foram submetidas à secção da base de um dos cornos uterinos (Grupo Operado, n = 7), enquanto as do Grupo Controle (n = 7) não foram submetidas a nenhuma intervenção cirúrgica. Ambos os grupos foram submetidos à IIP, sendo as fêmeas abatidas 5±1,2 dias após a última inseminação. Os sistemas genitais das fêmeas foram coletados, dissecados e o número de corpos lúteos contados em ambos os ovários. A recuperação dos embriões foi feita por meio de lavagem das tubas e cornos uterinos com solução de PBS (Phosphate Buffered Saline), após o que se avaliou os fluidos coletados em lupa para a identificação de embriões. Em ambos os grupos experimentais, foram encontrados embriões nos segmentos do sistema genital de ambos os lados. Apenas uma fêmea apresentou embriões nos segmentos em somente um dos lados no grupo operado. Diante dos resultados aqui observados, concluiu-se que a migração espermática no suíno pode ocorrer tanto por via retrógrada pelo útero quanto por migração intraperitoneal. Estes achados certamente contribuirão para aumentar a eficiência da técnica de IIP, sendo de grande valia para o aprimoramento da indústria suinícola.

Development and evaluation of deep intra-uterine artificial insemination using cryopreserved sexed spermatozoa in bottlenose dolphins (Tursiops truncatus)

Since its development in bottlenose dolphins, widespread application of AI with sex-selected, frozen-thawed (FT) spermatozoa has been limited by the significant expense of the sorting process. Reducing the total number of progressively motile sperm (PMS) required for an AI would reduce the sorting cost. As such, this research compared the efficacy of small-dose deep uterine AI with sexed FT spermatozoa (SEXED-SMALL; ~50×10(6)PMS, n=20), to a moderate dose deposited mid-horn (SEXED-STD, ~200×10(6)PMS; n=20), and a large dose of FT non-sexed spermatozoa deposited in the uterine body (NONSEXED-LARGE, 660×10(6)PMS, n=9). Ten of the 11 calves resulting from use of sexed spermatozoa were of the predetermined sex. Similar rates of conception (NONSEXED-LARGE: 78%, SEXED-STD: 60%, SEXED-SMALL: 57%) and total pregnancy loss (TPL: NONSEXED-LARGE: 28.6%; SEXED-STD: 41.0%; SEXED-SMALL: 63.6%) were observed across groups, but early pregnancy loss (EPL, <day 120 post-conception) was greater (P=0.04) for SEXED-SMALL (54.5%) compared to NONSEXED-LARGE (0%). Animals experiencing EPL were older (31.3 y, P=0.007) than those that calved (21.4y) or did not conceive (19.4y). After excluding females ≥25y, SEXED-SMALL (15.4%) had a tendency for having reduced calving rates compared to NONSEXED-LARGE (50.0%; P=0.08), while SEXED-STD did not differ (40.0%, 4/10; P=0.341). Current findings indicate that acceptable conception and calving rates using sexed FT spermatozoa are achieved after mid-horn deposition of 200×10(6) PMS, when used with females aged less than 25 y.

Emerging applications of sperm, embryo and somatic cell cryopreservation in maintenance, relocation and rederivation of swine genetics

Advances in porcine assisted reproductive technology (ART) make it possible to use cryopreserved sperm, embryos and somatic cells in the maintenance, relocation and regeneration of swine genetics. In this review, development of key application-limiting technology is discussed in each cell type, focusing on the efficiencies, ease of storage and transportation, and minimization of pathogen transmission. Methods to regenerate swine genetics and/or models using frozen sperm, embryos and somatic cells in combination with other porcine ARTs, such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and somatic cell nuclear transplantation (SCNT), are also discussed. The applications of these ARTs utilizing cryopreserved cells will greatly increase the efficiency as well as biosecurity for maintenance, relocation and rederivation of swine genetics/models.

New strategies of boar sperm cryopreservation: development of novel freezing and thawing methods with a focus on the roles of seminal plasma

Cryopreservation of boar spermatozoa offers an effective means of long-term storage of important genetic material. Many researchers have investigated how to improve reproductive performance by artificial insemination (AI) using cryopreserved boar spermatozoa. Recently, we and other groups reported that high conception rates (70-80%) can be achieved by AI with frozen-thawed boar spermatozoa using a modified temperature program during freezing, or a novel cryopreservation extender to improve sperm quality (including sperm survivability, motility, membrane status and fertilization ability) after thawing, or a novel sperm infusion method, deep intra uterine insemination. However, these techniques have not yet been used for commercial pig production. The variation in sperm freezability among boars or among ejaculations in an identical boar is one of the main reasons for this problem. In our previous study, it was revealed that some components of seminal plasma have a negative effect on the freezability of boar sperm. One of these factors is bacteria-released endotoxin (lipopolysaccharide: LPS). LPS binds to Toll-like receptor-4 (TLR-4) expressed on the sperm surface, resulting in induction of apoptosis. On the other hand, seminal plasma suppresses cryo-capacitation induced by thawing stress. On the basis of these findings, we designed a novel protocol of AI using frozen-thawed boar sperm.

Use of a novel double uterine deposition artificial insemination technique using low concentrations of sperm in pigs

Currently, the three most important non-surgical artificial insemination systems used in pigs are the conventional, the post-cervical (IUI), and the deep-intrauterine (DIUI) methods. In this study, a new system, termed double uterine deposition insemination (DUDI), which combines aspects of both IUI and DIUI, was evaluated. This method used a thinner, shorter and more flexible catheter than those normally used for DIUI and resulted in the deposition of semen post-cervically, approximately half-way along the uterine horn, thus potentially by-passing the threat of 'unilateral' insemination or pregnancy when using sperm of low concentration. The experiment was carried out over 8 weeks on a group of 166 sows, which were divided into seven groups, inseminated with semen of varying concentration, using the conventional system (control group) or by DUDI. There were no significant differences in fertility at day 35 post-insemination between the controls and the various DUDI sub-groups. Only sows inseminated with 500 million viable spermatozoa in a total of 30 mL of fluid using the DUDI system demonstrated decreased total litter sizes when compared to conventional insemination (P<0.001). While conventional insemination normally uses 2.5-3.5 billion sperm, the findings of this study suggest that DUDI can be used under 'field' conditions with sperm concentrations as low as 750 million spermatozoa in 50-30 mL without any detrimental effect on fertility or litter size. DUDI may provide a viable, robust alternative to IUI and DIUI, and has the potential to become incorporated into on-farm insemination systems.

Deep intra-uterine artificial inseminations using cryopreserved spermatozoa in beluga (Delphinapterus leucas)

Artificial insemination (AI) with liquid-stored spermatozoa and sperm cryopreservation using directional freezing (DF) have been successful in the beluga. This study built on this foundation to develop a deep intra-uterine AI technique with frozen-thawed semen in beluga. Forty-two ejaculates from one male were cryopreserved using DF technology and subsequently used for 10 insemination attempts with seven females. Percentage pre- and post-thaw progressive motility and viability were (mean +/- SD) 73.0 +/- 12.2, 38.4 +/- 8.8, 88.0 +/- 0.1, and 59.3 +/- 15.7%, respectively. A series of GnRH injections (3 x 250 microg, IV, 1.5 to 2 h apart) were used to induce ovulation, once a growing follicle >2.5 cm in diameter was visualized via trans-abdominal ultrasonography. Artificial insemination was performed at 30.1 +/- 3.8 h post-initial GnRH injection with semen deposited in the uterine horn, 92.6 +/- 16.2 cm beyond the genital opening using a flexible endoscope. The external cervical os (cEOS) was located beyond a series of 5 to 10 vaginal rings, 44.8 +/- 9.3 cm from the external genital opening. The internal bifurcation of the uterus was 27 +/- 6.8 cm beyond the cEOS. Ovulation occurred at 8.5 +/- 7.6 h post-AI. Two of 10 inseminations (20%) resulted in pregnancy. The first pregnancy resulted in twins; both calves were born 442 d after AI, with one surviving. The second pregnancy is ongoing. These findings represent the first successful application of AI using frozen-thawed semen in beluga, and are important examples of how assisted reproductive technologies can provide tools for the global management of threatened species.