Field data analysis of boar semen quality

This contribution provides an overview of approaches to correlate sow fertility data with boar semen quality characteristics. Large data sets of fertility data and ejaculate data are more suitable to analyse effects of semen quality characteristics on field fertility. Variation in fertility in sows is large. The effect of semen factors is relatively small and therefore impossible to find in smaller data sets. Large data sets allow for statistical corrections on both sow- and boar-related parameters. Remaining sow fertility variation can then be assigned to semen quality parameters, which is of huge interest to AI (artificial insemination) companies. Previous studies of Varkens KI Nederland to find the contribution to field fertility of (i) the number of sperm cells in an insemination dose, (ii) the sperm motility and morphological defects and (iii) the age of semen at the moment of insemination are discussed in context of the possibility to apply such knowledge to select boars on the basis of their sperm parameters for AI purposes.     

Updates on Reproductive Physiology, Genital Diseases and Artificial Insemination in the Domestic Cat

Reproduction in the domestic cat is characterized by large individual variations in the female oestrous cycle and in male semen quality. The female cat reproduction is strongly influenced by season, and new data suggest that it is possible that season also affects male fertility. Repeated periods of oestrus and spontaneous ovulation may lead to degenerative endometrial changes causing infertility. For artificial insemination (AI), induction of ovulation is necessary in the absence of the mating stimuli. The large variation in the relationship between follicular growth and timing of expression of oestrus complicates, however, timing of ovulation induction. Stress may lead to progesterone secretion by the adrenal glands and possibly have a negative impact on early pregnancy. The large individual variation in semen quality makes fertility evaluation and feline semen conservation a challenge. For AI, the semen can be deposited in the cranial vagina, the uterus or in the uterine tubes. Intrauterine insemination results in higher pregnancy rates than intravaginal but is more complicated. Surgical intrauterine or intratubal insemination has resulted in the birth of kittens, but is an invasive procedure that is not allowed in all countries. Transcervical intrauterine insemination with frozen-thawed semen has, however, recently resulted in the birth of kittens.     

Genetic Parameters for Semen Production Traits in Austrian Dual-Purpose Simmental Bulls

Genetic parameters were estimated for semen production traits collected in an Austrian AI centre in the years 2000-2004. In total, 12,746 ejaculates from 301 Austrian dual-purpose Simmental (Fleckvieh) AI bulls were examined considering different effects on ejaculate volume, sperm concentration, percentage of viable spermatozoa in the ejaculate, total spermatozoa per ejaculate and motility. The model for genetic parameter estimation included the fixed effects age of bull, collection interval, number of collections on collection day, bull handler, semen collector, year and month of collection, a random additive genetic component and a permanent environmental effect. Correlations between estimated breeding values for semen traits and male fertility from the routine evaluation were calculated. The fertility trait considered in the routine evaluation is non-return rate 90 for the first insemination. All semen production traits were moderately heritable. Heritabilities for volume, concentration, percentage of viable spermatozoa, total number of spermatozoa and motility were 0.18, 0.14, 0.10, 0.22 and 0.04, respectively. Correlations between breeding values for semen quality traits and routinely estimated breeding values for male fertility were low and ranged from 0.08 to 0.17 indicating that semen production traits are rather poor predictors of male fertility.     

猫人工授精技术研究进展

人工授精技术是一种较先进的辅助生殖技术,可提高繁殖育种的效益,但因猫类较独特的生殖特点,其人工授精技术发展受限。近年来,科研人员和临床工作者借鉴其他物种相对成熟的人工授精技术,结合猫类生殖特点,对猫人工授精过程中精液采集、精液品质评估、精液保存、刺激母猫排卵方式及具体的人工输精等相关技术进行了优化和创新,如开发了新颖实用的尿导管法采精技术以采集猫精液;在传统精液品质评估的基础上,配合使用荧光染色技术、流式细胞技术及体外受精技术对猫精液品质进行评估;探索不同冷冻液配方及冷冻程序对猫精液保存效果的影响,并尝试使用超快速冷冻法保存公猫遗传物质;研究使用不同种类及不同剂量的激素对诱导母猫发情和排卵效果的差异,以及不同输精部位、方法及时机对母猫妊娠结果的影响等。尽管其中一些新技术与方法已在试验动物中彰显出了其实际应用潜力,但当下依旧还存在操作相对复杂、成本较高、效果低于预期等问题,导致目前猫人工授精技术的应用较局限,不如在犬或其他动物中应用广泛,未来还需更进一步研究和探索才能满足临床实际应用的需要。文章就上述猫人工授精技术中各个方面的研究进展进行了综述,以期为该技术的进一步研究和应用提供参考。     

浅谈猪精液保存在人工授精中的发展与展望

在世界上主要的猪肉生产国中,猪人工授精(AI)技术的应用率在90%以上。尽管猪冷冻精液技术在不断进步,但由于其效率不高,在猪场实际生产中并不多见使用。在猪人工授精技术中,液态精液是目前应用最广泛的精液,与传统的牛冷冻精液不同,其独特的精子微胶囊保护膜技术,可以对猪精子进行更加完善的液态保存,因此液态精液是目前猪人工授精使用的主要方式。文章综述了猪精液保存技术在人工授精中的应用,并展望了今后的发展方向,为人工授精技术助力恢复生猪生产提供参考。     

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.     

猪深部输精技术应用研究进展

常规子宫颈人工授精(cervical artificial insemination,CAI)技术输精量大,存在浪费和不经济的问题,尤其在使用高附加值的精液产品时更为突出。近年来,一种高效利用猪精液的深部输精技术得到了研究和应用,这种技术与定时输精技术相结合,直接将精液输送至子宫体、子宫角和输卵管内,减少了每头母猪受孕所需精子数目,大幅度提高了良种公猪的利用价值,有助于实现冷冻保存精液和性控精液在养猪生产上的商业化应用。作者概述了猪人工授精中3种深部输精技术在液态保存、冷冻保存和性控精液上的研究和应用情况。无论实施哪种输精技术,公猪繁殖力、精子活力、母猪的饲养管理、输精时间和人工授精技术操作的规范性都是提高受胎率必须要考虑的因素。     

Advances in the Research and Application of Artificial Insemination to Equids in China: 1935–2012

China was one of the first countries to use artificial insemination (AI) in equids, and it achieved international recognition for its widespread application of AI to commercial horse breeding. This article reviews the history of equine AI in China. The technique originated from the high demand for horses to be used in agriculture, transportation, and the military. Artificial insemination was identified as an ideal tool for Chinese horse breeding to improve the productivity of native horses, especially during 1950-1970. Presently, AI is still practiced commonly in China, and it includes the use of fresh semen and transported cooled semen. The use of frozen semen has also been resumed to broaden the range of elite Sporthorse stallions and to preserve threatened or endangered native breeds. Accurate prediction of the optimum time for insemination depended mainly on transrectal palpation of the mare's ovaries. In addition to controlled methods of insemination, factors like volume and number of spermatozoa in the inseminate and timing and frequency of insemination were optimized to accomplish high fertility rates in the field. Production of hinnies and mules for agricultural labor and donkeys for meat and hide gelatin stimulated a nationwide upsurge of research into the reproductive physiology of and AI technology in donkeys. In the future, there will be further increases in the use of traditional and modern AI techniques in the breeding of Chinese equids.     

Fertility Results of Artificial Inseminations Performed with Liquid Boar Semen Stored in X-CellTM vs BTS Extender

The objective of the present field study was to compare the fertility results for boar semen diluted in X-cell stored up to 4-5 days before artificial insemination (AI) with semen diluted in Beltsville thawing solution (BTS) used for AI following 2-3 days of storage (where the first day being the collection day). A total number of 2601 double inseminations in Norwegian herds were included in this two-trial study. All the boars used in the study were mature cross-bred Norwegian Landrace x Duroc (LD), which were routinely used for AI in Norway. The inseminated gilts and sows were Norwegian Landrace x Yorkshire (LY). The AI doses contained 2.5 billion spermatozoa, and consisted of a mixture of semen from three, occasionally four, boars (i.e. heterospermic semen). Fertility was measured in terms of the likelihood of farrowing and subsequent litter size. The fertility of the semen in both of the extenders was satisfactory and no significant differences were found either in semen stored 4-5 days in X-cell compared with 2-3 days in BTS or in semen stored 2-3 days in X-cell compared with 2-3 days in BTS. The storage capability findings for the long-term extender X-cell could significantly simplify the practical issues of semen production and the distribution of AI doses containing 2.5 billion spermatozoa. However, in pig production systems where all semen is used within 2-3 days, the short-term extender BTS is as good as the more expensive extender X-cell.     

The Predictive Value of Porcine Seminal Parameters on Fertility Outcome under Commercial Conditions

The aim of this study was to address the question of whether differences in farrowing rate and litter size after the use of different ejaculates could be predicted using the standard semen parameters under commercial conditions. In this study, a total of 1818 sows were used to evaluate the fertility predictive value of different sperm parameters. Logistic regression analysis (univariate and multivariate) was used to correlate the dichotomous farrowing rate data to the sperm parameters. Linear regression was also used to determine the relationship between litter size and semen parameters (Pearson correlation and multiple regression). Receiver-operating curves (ROC) were used to determine the overall performance characteristics of each semen variable in the logistic regression model. Semen analysis, under commercial conditions, allows to identify ejaculates with very low fertility potential but the pre-selection of the samples, the high number of sperm per doses and the high quality of the semen used in artificial insemination (AI) programmes reduces the variability. Therefore, it is unlikely to detect fertility differences associated with seminal parameters.     

猪精液超低温冷冻保存研究进展

猪人工授精(AI)技术已经广泛应用于畜牧业生产,但精液来源基本是17℃保存的新鲜猪精液,不利于精液长期保存和猪种资源保存。超低温冷冻保存技术是猪精液长期保存最有效的方法,冷冻精液可以实现不同地区、不同国家优良种猪精液间的交流,从而大大提高猪种资源的利用率,但冷冻解冻后的精液质量较差,受胎率、窝产仔数远低于鲜精,极大地限制了猪精液冷冻保存技术的广泛应用。本文综述了猪精液冷冻保存研究概况、猪精液冷冻损伤机理和猪精液冷冻保存影响因素,以期为猪精液超低温冷冻保存研究提供新的思路和方法。     

Biological markers of boar fertility

The semen evaluation techniques used in most commercial artificial insemination centers, which includes sperm motility and morphology measurements, provides a very conservative estimate of the relative fertility of individual boars. As well, differences in relative boar fertility are masked by the widespread use of pooled semen for commercial artificial insemination (AI) in many countries. Furthermore, the relatively high sperm numbers used in commercial AI practice usually compensate for reduced fertility, as can be seen in some boars when lower numbers of sperm are used for AI. The increased efficiency of pork production should involve enhanced use of boars with strong reproductive efficiency and the highest genetic merit for important production traits. Given that the current measures of semen quality are not always indicative of fertility and reproductive performance in boars, accurate and predictive genetic and protein markers are still needed. Recently, significant efforts have been made to identify reliable markers that allow for the identification and exclusion of sires with reduced reproductive efficiency. This paper reviews the current status of proteomic and genomic markers of fertility in boars in relation to other livestock species.     

Is sperm DNA fragmentation a good marker for field AI bull fertility?

This paper aimed at investigating the potential use of sperm DNA fragmentation (SDF) to improve the routine screening of infertility of Holstein bulls. Cryopreserved sperm samples from 201 Holstein bulls provided by an AI center were used in the analyses of SDF at 0 (SDF_0) and 6 (SDF_6) h of incubation at 37°C. A refinement of the sperm chromatin dispersion test implemented in the Sperm-Halomax kit was employed to measure SDF. Records on routinely collected semen traits (volume, concentration, mass and individual motility evaluated in the fresh ejaculate, and individual motility in post-thawed semen straws) were provided by the AI center. Artificial insemination bull fertility was obtained from official field recording as successful or failed insemination. The results show that the average SDF was low (around 3.5%) at 0 and 6 h of incubation. A moderate effect of inbreeding depression was found. Estimated heritability for SDF traits were moderately high (0.41 and 0.29 for SDF_0 and SDF_6, respectively) and estimated repeatability of SDF measures in the same animal were high (0.73 and 0.70 for SDF_0 and SDF_6, respectively). An overall estimated service bull value (ESBV) obtained through statistical modeling that allowed for adjustment of systematic environmental effects not specific to a bull and of the female contribution to fertility, and the estimated genetic values (EGV) were obtained from field-recorded AI information. The ESBV and EGV were also obtained for all semen traits. Moderately large and negative Pearson correlation coefficients were observed between SDF traits and male fertility ranging from (-0.43 to -0.50; P <0.001). Results of stepwise regression analyses showed that SDF_6 had the largest partial r(2) (0.15 to 0.26) among all semen characteristics. Overall, the selected semen traits explained 25% and 31% of the observed variability in bull fertility measured as EGV and ESBV, respectively. When looking at the predictive ability of bull fertility categories, the results of discriminant and logistic regression analyses showed that low-fertility bulls (those in the 10th or lower percentile in the fertility distribution) can be accurately identified by using measures of SDF alone or in combination with sperm motility. Values of SDF around 7% to 10% could be used as indicators of low AI success.     

FERTILITY OF FROZEN BOAR SEMEN USED FOR AI IN COMMERCIAL SETTINGS

Surgical insemination was the least efficient means to procure offspring (27% farrow rate). However, it offers to be an effective means for generating offspring from limited semen supplies or semen having high value (i.e. genetic merit or gender selected sperm). Transcervical AI resulted in an overall 40% farrow rate. However, there was a significant farm effect observed and this was anticipated in considering the variation in management and personnel practices.
The application of frozen boar semen for commercial practice has merit. Although the fertility of frozen semen is below that of fresh semen, it is a low cost and efficient method for introgressing new germplasm (genetics) into a current genetic base. With respect to seedstock suppliers, the lowered fertility associated with frozen semen is acceptable when it is looked upon as a means to introduce new genetics for research purposes.     

Bovine sperm selection procedure prior to cryopreservation for improvement of post-thawed semen quality and fertility

Background: The application of cryopreservation and artificial insemination technology have contributed to the advancement of animal reproduction. However, a substantial proportion of spermatozoa undergoes alterations and loses their fertility during cryopreservation, rendering the frozen-thawed semen impractical for routine use.Cryopreservation is known to reduce sperm lifespan and fertility. Variation in cryosurvival of spermatozoa from different sires and even with the individual sire is common in artificial insemination(AI) centers. Our goal is to improve post-thawed semen quality by optimization of cryopreservation technique through sperm selection prior to cryopreservation process.Results: Our strategy of sperm selection based on rheotaxis and thermotaxis(SSRT) on macrosale in a rotating fluid flow demonstrated the ability to maintain the original pre-freezing structural integrity, viability and biological function related to fertilization competence. This strategy has a positive effect on the cryosurvival and fertilizing abilities of spermatozoa as supported by the improvement on pregnancy rate of Japanese Black heifers and Holstein repeat breeders. This technique protected further sublethal damage to bovine spermatozoa(higher %cryosurvival than the control) and resulted in the improvement of DNA integrity. Prefreeze selected spermatozoa demonstrated slower and controlled capacitation than unprocessed control which is thought to be related to sperm longevity and consequently to appropriate timing during in vivo fertilization.Conclusions: These results provide solid evidence that improvement of post-thawed semen quality by SSRT method is beneficial in terms of cryosurvival, longevity of post-thawed sperm, and optimization of in vivo fertilization, embryo development and calving as supported by the favorable results of field fertility study.     

Current challenges in sheep artificial insemination: A particular insight

Ovine artificial insemination (OAI) is not commonly performed because of specific problems related to semen application techniques, leading to highly variable results. The ideal methodology (frozen‐thawed semen/vaginal route) is unfeasible under field conditions due to the cervix morphology of the ewe, which prevents the process of intrauterine insemination necessary to obtain acceptable results. Currently, OAI commercial programmes use superficial cervical insemination, CAI (vaginal), with chilled semen (15°C) and intrauterine insemination, LAI (laparoscopic), with frozen‐thawed semen. The ability to improve upon these contrasting techniques may be derived from examining certain poorly studied factors such as insemination time, productive state of females and alternatives of seminal preservation, some of which we reviewed in this work. This interim solution will remain in use until AI by the vaginal route with frozen‐thawed semen is developed, but it poses new challenges in optimizing the freezing of the sperm and adapting the cervical (CAI) and/or transcervical intrauterine AI (TCAI). In this review, we address the current problems and evaluate their methodological (mechanical) and chemical (dilation) alternatives. Currently, TCAI is a methodologically complex technique with poor fertility results, so further studies are needed to improve the logistics of this procedure and the results of its application.     

Laboratory Semen Assessment and Prediction of Fertility: still Utopia?*

Finding a laboratory test reliable enough to predict the potential fertility of a given semen sample or a given sire for artificial insemination (AI) is still considered utopian, as indicated by the modest correlations seen between results obtained in vitro and field fertility. Male fertility is complex, and depends upon a heterogeneous population of spermatozoa interacting at various levels of the female genital tract, the vestments of the oocyte, and the oocyte itself. For this reason, laboratory assessment of semen must include the testing of most sperm attributes relevant for fertilization and embryo development, not only in individual spermatozoa but within a large sperm population as well. Strategies for the discovery of in vitro predictors of semen fertility require evaluations of low sperm doses for AI, so that differences in innate in vivo fertility can be accurately detected.     

Application of computer-assisted semen analysis to explain variations in pig fertility

Sperm quality is often evaluated through computer-assisted semen analysis (CASA) and is an indicator of boar fertility. The aim of this research was to study the relationship between CASA motility parameters and fertility results in pigs. Insemination records and semen parameters from a total of 45,532 ejaculates collected over a 3-yr period were used. The statistical model for analysis of fertility data from these inseminations included factors related to sow productivity. The boar- and semen-related variance (direct boar effect) were corrected for the effects of individual boar, genetic line of the boar, age of the boar, days between ejaculations, number of sperm cells in an ejaculate, number of sperm cells in an insemination dose, and AI station. The remaining variance was analyzed if semen motility parameters had a significant effect. This analysis revealed significant (P < 0.05) effects of progressive motility, velocity curvilinear, and beat cross frequency on farrowing rate (FR). Total motility, velocity average path, velocity straight line, and amplitude of lateral head displacement affected (P < 0.05) total number of piglets born (TNB). Boar- and semen-related parameters explained 5.3% of the variation in FR and 5.9% of the variation in TNB. Motility parameters, measured by CASA, explained 9% of the boar- and semen-related variation in FR and 10% of the boar- and semen-related variation in TNB. Individual boar and genetic line of the boar affected (P < 0.0001) the variation in FR and TNB. No differences (P > 0.05) were observed between effects of AI stations on fertility outcome, underscoring the objectivity of the CASA system used. Motility parameters can be measured with CASA to assess sperm motility in an objective manner. On the basis of the motility pattern, CASA enables one to discriminate between the fertilizing capacity of ejaculates, although this depends on the genetic line of the boar used in AI stations.     

Semen collection and artificial insemination in the common piping guan (Pipile cumanensis cumanensis): potential applications for Cracidae (Aves: Galliformes).

The common piping guan (Pipile cumanensis cumanensis) is serving as a model for assisted reproductive techniques (ARTs) in Cracidae (Aves: Galliformes). Manual collection methods used in domestic birds and other exotics were modified to optimize quality and quantity of fresh semen samples. In addition, a method to subjectively assess semen quality on the basis of its color, clarity, and consistency was developed to serve as a tool when laboratory equipment is not available. In a species where only two eggs per clutch is typical, predictability of the date of the first egg is critical to ensure adequate inseminations before oviposition. An increase in both the distance between the female's pubic bones and degree of abdominal swelling indicated optimal time to initiate artificial insemination (AI) and allowed the number of semen samples used to fertilize the first egg in the clutch to be minimized while ensuring its fertility. In three separate AI trials, a total of four fertile eggs were produced, a first for cracids. Two of the four fertile eggs hatched successfully, and the chicks' parentages were confirmed using DNA fingerprinting. This study represents the first published account of the use of ARTs in Cracidae and forms the basis for future developments (e.g., AI of frozen-thawed semen) aimed at optimizing genetic management of cracids in ex situ breeding programs.     

Review on international trade with boar semen

For more than 40 years, AI (artificial insemination) has been carried out with pigs. In some countries, it constitutes since the 1990 s the dominant procedure with piglet production to fertilize the sow. This procedure of insemination with fresh semen has become prevalent in all countries on a worldwide basis with an important pig meat production, with the exception of China. Meanwhile, up to 90% of the sows have been artificially inseminated. The trend is still upwards. As the need of pig meat and thus the production continues to increase, one can proceed on the assumption that the number of semen doses, which is necessary for this procedure, will likewise increase correspondingly. Until now, the trade beyond borders has only been marginal. An improvement in the sense of a longer shelf life for semen doses is indispensable for the trade over longer distances.