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.     

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

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

Recent advances in bovine sperm cryopreservation techniques with a focus on sperm post‐thaw quality optimization

Sperm cryopreservation facilitates the storage and transport of germplasm for its use in artificial insemination (AI) and other advanced reproductive technologies. The cryopreservation process can damage sperm and compromise functionality. Several cryobiological studies have found that the physical and biological factors that affect sperm survival at low temperatures during the cryopreservation process often involve the integrity of sperm membrane. In this review, the behaviour of the sperm membrane against cooling, cold shock, ice crystal formation, oxidative stress, osmotic changes, reorganization of the lipid bilayer and addition of cryoprotective agents (CPA) is discussed. In addition, the phenomenon of reactive oxygen species (ROS) and its relationship with the cryopreservation process is also described. Semen cryopreservation techniques have progressed slowly in past years, and the current performance, measured as post‐thawed survival, is not very different compared to past decades. Recent advances in understanding the structure of the cell membrane, its function and metabolism have driven to new conservation systems, including lyophilization and vitrification. However, none of these technologies is commercially available, although its future appears very promising.     

Control of the estrous cycle in the mare

All current approaches to manipulating the reproductive biology of the nonpregnant mare are discussed.     

The potential risk of infectious disease dissemination via artificial insemination in swine

Artificial insemination (AI) is one of the most widely used assisted reproductive technologies in swine. To maintain a healthy semen trade, it is crucial that diligence be given to managing and minimizing the chance of extended semen playing an epidemiological role in the transmission of infectious disease. In swine, pathogens of primary importance, which may be transmitted through semen include Aujeszky's disease, brucellosis, chlamydophilosis, porcine circovirus type 2, classical swine fever, Japanese encephalitis, leptospirosis, parvovirus, porcine reproductive and respiratory syndrome, rubulavirus, foot-and-mouth disease and swine vesicular disease. This paper will summarise the current state of knowledge pertaining to these pathogens in relation to swine AI.     

Optimizing female allocation to reproductive technologies considering merit,inbreeding and cost in nucleus breeding programmes with genomic selection

Female reproductive technologies such as multiple ovulation and embryo transfer (MOET) and juvenile in vitro fertilization and embryo transfer (JIVET) have been shown to accelerate genetic gain by increasing selection intensity and decreasing generation interval. Genomic selection (GS) increases the accuracy of selection of young candidates which can further accelerate genetic gain. Optimal contribution selection (OCS) is an effective method of keeping the rate of inbreeding at a sustainable level while increasing genetic merit. OCS could also be used to selectively and optimally allocate reproductive technologies in mate selection while accounting for their cost. This study uses stochastic simulation to simulate breeding programmes that use a combination of artificial insemination (AI) or natural mating (N), MOET and JIVET with GS. OCS was used to restrict inbreeding to 1.0% increase per generation and also to optimize use of reproductive technologies, considering their effect on genetic gain as well as their cost. Two Australian sheep breeding objectives were used as an example to illustrate the methodology—a terminal sire breeding objective (A) and a dual‐purpose self‐replacing breeding objective (B). The objective function used for optimization considered genetic merit, constrained inbreeding and cost of technologies where costs were offset by a premium paid to the seedstock breeder investing in female reproductive technologies. The premium was based on the cumulative discounted expression of genetic merit in the progeny of a commercial tier in the breeding programme multiplied by the proportion of that benefit received by the breeder. With breeding objective B, the highest premium of 64% paid to the breeder resulted in the highest allocation of reproductive technologies (4%–10% for MOET and 19%–54% for JIVET) and hence the highest annual genetic gain. Conversely, breeding objective A, which had a lower dollar value of the breeding objective and a maximum of 5% mating types for JIVET and zero for MOET were optimal, even when highest premiums were paid. This study highlights that the level of investment in breeding technologies to accelerate genetic gain depends on the investment of genetic improvement returned to the breeder per index point gain achieved. It also demonstrates that breeding programmes can be optimized including allocation of reproductive technologies at the individual animal level. Accounting for revenue to the breeder and cost of the technologies can facilitate more practical decision support for beef and sheep breeders.     

Capacitation and capacitation-like sperm surface changes induced by handling boar semen

Since it has been well recognized that reproductive technologies, such as cryopreservation and sex-sorting, have a detrimental impact on sperm quality. These procedures cause sperm membrane destabilization which resembles that of capacitation. The pathways of this complex biochemical event are slowly unravelling, including the vital role of coating and decoating factors on the sperm surface. Characterization of these factors is leading to the development of novel surface manipulation techniques to stabilize the sperm membrane during handling. The possible application of these for assisted pig reproduction is discussed.     

Equine Embryo Sexing and Ultrasonographic Foetal Sexing – Interests and Applicability

The ability to choose the sex of the offspring is of upmost economic importance for horse breeders. Unlike other species, horses present several reproductive peculiarities that interfere with assisted reproductive technologies used in other large animals (such as bovine) and make them difficult to apply. Thus, there is a great interest to determine the sex of the offspring as soon as possible. This has led to the development of several technologies to serve this purpose, which can be classified into two categories. One is equine embryo sexing by either non‐invasive biotechnological methods, such as monitoring of X‐linked enzymes before X chromosome inactivation and detection of sex‐specific antigen, or by invasive biotechnological methods, such as cytogenetic analysis and polymerase chain reaction (PCR). The other one is equine foetus sexing using ultrasound scanning in different stages of its development (early, mid or late), by different approaches (transrectally or transabdominally). This can be performed with classic B‐mode ultrasound machines or using 3D‐mode and Doppler‐mode scanners. This review article offers a comprehensive overview of the current status of these procedures as well as an assessment of their interests and applicability.     

提高母猪繁殖利用率的综合技术措施

本文从建立和保持合理结构的母猪群体，及时淘汰生产性能低的母猪，加强母猪各饲养阶段的管理，严格控制繁殖阻碍性疫病等方面，总结了提高母猪繁殖利用率的相关技术措施，并提出了有效增加母猪窝产仔数的技术措施，对提高母猪生产具有一定指导意义。     

牦牛同期发情技术研究进展

同期发情是动物繁殖生物技术之一,已广泛应用于畜牧生产中。本文综述已有同期发情技术在牦牛生产中的研究成果,针对目前研究与应用中存在的主要问题,提出牦牛同期发情技术的研究方向及应用前景。     

Integrating molecular biology into the veterinary curriculum

The modern discipline of molecular biology is gaining increasing relevance in the field of veterinary medicine. This trend must be reflected in the curriculum if veterinarians are to capitalize on opportunities arising from this field and direct its development toward their own goals as a profession. This review outlines current applications of molecular-based technologies that are relevant to the veterinary profession. In addition, the current techniques and technologies employed within the field of molecular biology are discussed. Difficulties associated with teaching a subject such as molecular biology within a veterinary curriculum can be alleviated by effectively integrating molecular topics throughout the curriculum, pitching the subject at an appropriate depth, and employing varied teaching methods throughout.     

Reproduction in Domestic Buffalo

The domestic buffalo is an indispensable livestock resource to millions of smallholder farmers in developing countries, particularly in Asia. Although its reproductive biology is basically similar to that of cattle, there are important differences and unique characteristics that need to be considered in order to apply modern reproductive technologies to improve its productivity. Under most smallholder production systems, the reproductive efficiency of buffalo is compromised by factors related to climate, management, nutrition and diseases. However, when managed and fed properly, buffalo can have good fertility and provide milk, calves and draught power over a long productive life. The basic technical problems associated with artificial insemination in buffalo were largely overcome two decades ago, but the technology has not had the expected impact in some developing countries, because largely of infrastructural and logistic problems. Approaches involving the use of hormones for treating anoestrus and for synchronizing oestrus have had varying rates of success, depending on the protocols used and the incidence of underlying problems that cause infertility. Embryo technologies such as multiple ovulation embryo transfer, in vitro embryo production, cryopreservation and cloning are being intensively studied but have had far lower success rates than in cattle. Improving the productivity of buffalo requires an understanding of their potential and limitations under each farming system, development of simple intervention strategies to ameliorate deficiencies in management, nutrition and healthcare, followed by judicious application of reproductive technologies that are sustainable with the resources available to buffalo farmers.     

Manipulation of Domestic Animal Embryos and Implications for Development

Assisted reproductive technologies, as applied to domestic animals, can exert both novel and wide‐ranging influences on the development, viability and welfare of offspring. Some of the changes are evident immediately or soon after the time at which a manipulative procedure is carried out, while other changes may not be evident until later in development or, perhaps, may remain undetected throughout an animal's lifetime. The present review explores some of the consequences – in terms of foetal, placental, neonatal and post‐natal effects – of exposing embryos of cattle, sheep and other species to in vitro culture per se or, during culture, to physically invasive technologies including gene injection and nuclear transfer. The innate sensitivity of oocytes and recently fertilized eggs to their in vitro environment is illustrated by an examination of the later developmental repercussions resulting from apparently innocuous choices related to in vitro culture medium formulations. In contrast, an inherent resilience and paradoxical readiness to resume development following the traumas of nuclear transfer procedures is also in evidence. The extent to which assisted reproductive technologies will succeed, where relevant, in the domestic animal sector will be influenced by our appreciation of embryo requirements, for both short‐ and long‐term developmental fitness, during their earliest developmental stages. Evidence of species‐specific needs is testimony to the challenges ahead. Ultimately, our ability and inclination to resolve the limitations associated with current procedures will probably be greatly enhanced if predictive indicators (genetic, epigenetic or functional markers) of later developmental fitness can be identified.     

甘南玛曲草地退化现状及恢复重建初探

通过对甘南玛曲草地退化现状的分析，探讨草地退化与植被恢复重建的技术措施，结果表明：退化严重的草地通过封育、补播、施肥、灭鼠等综合治理以及各单项技术的科学组装配套，可有效地治理退化严重的草地。     

甘南玛曲草地退化现状及恢复重建初探

通过对甘南玛曲草地退化现状的分析,探讨草地退化与植被恢复重建的技术措施,结果表明:退化严重的草地通过封育、补播、施肥、灭鼠等综合治理以及各单项技术的科学组装配套,可有效地治理退化严重的草地。     

肉牛遗传育种与繁殖技术应用现状

通过介绍我国肉牛遗传育种与繁殖技术方法,概述了数量遗传学、育种值估计、常规育种、分子育种技术等在肉牛育种、生产领域中的应用现状,并对人工授精技术、胚胎移植技术、胚胎分割技术、性别控制技术、体外授精技术和克隆技术等繁殖技术在肉牛科研与生产中的应用进行了介绍,以期为肉牛遗传育种与繁殖技术研究及生产提供参考.     

鸭繁殖性状分子遗传研究进展

本文着眼于现代分子数量遗传新技术在鸭遗传育种中的应用前景,对鸭繁殖性状的分子遗传研究进行综述。介绍繁殖相关激素和调节因子的基因研究、与肝脏及卵巢中脂肪酸代谢相关功能基因的研究、与生长发育相关基因的研究等进展情况;同时介绍鸭分子遗传标记的开发和连锁图谱构建等方面的新进展。     

Importance of assisted reproductive technologies in the conservation of wild, rare or indigenous ungulates: review article

Biodiversity is increasingly threatened by intensive agriculture, environmental pollution, extinction of natural habitats and several other factors. Several mammalian species including ungulates have disappeared or are threatened by extinction. However, ungulates play an important role both in the ecosystem and in the economy. In general, species or breeds are considered endangered if their population does not exceed 1,000 individuals. In these cases conservation programmes should be initiated in order to maintain or even increase their number. This review deals with the possibilities and limitations of assisted reproductive technologies (ART) in the conservation of ecologically valuable wild, rare and indigenous ungulates. The methods discussed here are artificial insemination, cryopreservation of semen and embryos, embryo recovery and transfer, in vitro production of embryos, as well as micromanipulation techniques including sperm injection, assisted hatching and cloning. Some of these procedures are already being exploited in the breeding of farm ungulates, but more basic information about the reproductive patterns of wild, rare and indigenous animal species is needed before the routine use of ARTs.     

我国兽用化学药物的研究开发及所面临的挑战

讨论了创新化学兽药的类型和特点，论述了创新化学兽药研究开发的理论和发展现状及趋势，提出了我国兽用化学药物研究开发的策略。