Embryo Transfer Technology Research Articles

Production of commercial valuable products using transgenic technology

Commercialization of animal biotechnology is a wide-ranging topic for discussion. In this paper, we will attempt to review embryo transfer (ET) and related technologies that relate to food-producing mammals. A brief review of the history of advances in biotechnology will provide a glimpse to present and future applications.Commercialization of animal biotechnology is presently taking two pathways. The first application involves the use of animals for biomedical purposes. Very few companies have developed all of the core competencies and intellectual properties to complete the bridge from lab bench to product.The second pathway of application is for the production of animals used for food. Artificial insemination (AI), embryo transfer, in vitro fertilization (IVF), cloning, transgenics, and genomics all are components of the toolbox for present and future applications. Individually, these are powerful tools capable of providing significant improvements in productivity. Combinations of these technologies coupled with information systems and data analysis, will provide even more significant change in the next decade.Any strategies for the commercial application of animal biotechnology must include a careful review of regulatory and social concerns. Careful review of industry infrastructure is also important. Our colleagues in plant biotechnology have helped highlight some of these pitfalls and provide us with a retrospective review.In summary, today we have core competencies that provide a wealth of opportunities for the members of this society, commercial companies, producers, and the general population. Successful commercialization will benefit all of the above stakeholders.

State of the art in sheep-goat embryo transfer

Considerable advances have been made in the last 25 yr in sheep and goat embryo production and transfer technology. This presentation covers the procedures used to overcome the variability of ovarian response after treatment with exogeneous gonadotropins, the asynchrony of ovulations, failure of fertilization in females showing a high ovulatory response, and the side-effects of repeated treatments (surgical trauma, gonadotropins and their antibodies). In the ewe, prior antigonadotrophic pretreatment results in a significant gain in ovulation rate due to the elimination of nonresponses and in a two-fold increase in embryo yield. A better comprehension of the relationships between oocyte quality and follicular characteristics after superovulation can be gained using in vitro techniques. This knowledge will subsequently be used for the optimization of embryo production needed for the genetic improvement of livestock and the development of new biotechnologies.

Parentage assessment of an IVF calf from Bubalus bubalis by DNA fingerprinting

We used two synthetic oligodeoxyribonucleotide probes, OAT18 and OMS1 comprising (TGG) 6 and (GGTA) 4 repeat motifs, respectively, in combination with HinfI enzyme for DNA fingerprinting of a calf born from embryo transfer technology, its surrogate mother (SM) and the sperm donor (bull). Of the two polymorphic probes, OAT18 was found to be more informative for correctly establishing the parentage status of the in-vitro fertilized (IVF) calf and demonstrated the genetic relationship of the SM with the bull. Two types of cluster analysis, SAHN clustering and neighbour joining tree, performed with similarity indices of these individuals produced by OAT18 probe were found to be different. Using the SAHN cluster method, SM was found to be genetically closer to the bull than to IVF calf, whereas using the neighbour joining method, IVF was closer to bull than SM. A similar result was obtained by SAHN clustering with OMS1 probe. The relevance of this approach for parentage control in the context of animal biotechnology is described.

Embryo transfer and related technologies in sheep reproduction

This paper reviews the status of embryo transfer and the major technologies applied to preimplantation of embryos in sheep. Embryo production from superovulated ewes is hindered by an unpredictable response to hormonal treatment. Progress in this area should be expected by an appropriated control of follicular development with gonadotropin-releasing hormone (GnRH) agonist or antagonist prior to gonadotrophin administration. Simple protocols for the cryopreservation of sheep embryos by vitrification are already available and the development of frozen-thawed blastocysts to term is close to the fresh ones. Further research is required to identify factors able to promote the maturation in vitro of oocytes, namely those obtained from prepubertal animals. Semen and embryo sexing procedures are available in cattle although much less attention was paid to their application to sheep. Among all the reproductive technologies, cloning with embryonic and foetal cells has progressed dramatically in sheep and nuclear transfer has been used to produce transgenic animals as an alternative to pronuclear injection. The production of the first lamb cloned from a somatic cell opened new opportunities in animal breeding as well as exciting lines of basic research. The overall conclusions are that, apart from superovulation, the application of in vitro technologies is likely to evolve rapidly and once applied, a great impact on traditional and new animal productions should be expected. However, a better understanding of the changes in gene expression, induced in embryos by different in vitro manipulation procedures, is necessary to prevent abnormal foetal development.

Views on the potential impact of cloning on animal breeding and production

The potential benefits of cloning domestic animals in animal breeding and production are considered. It is concluded that cloning will not make a significant contribution to increasing the rate of genetic gain in selection programmes. It seems that only marginal advantages can be derived from the use of cloning in other areas of livestock production. If costs are reduced and embryo transfer technology continues to advance, the dissemination of genetic material in the form of cloned embryos could be a reality. It will lead to the introduction of greatly increased risk in animal production and the consequences can be substantial.

Factors associated with variation in the superovulatory response of cattle.

Kafi, M., McGowan, M.R., 1997. Factors associated with variation in the superovulatory response of cattle. Anim. Reprod. Sci. Variability in the superovulatory response of cattle is still one of the major limiting factors in extensive usage of embryo transfer technology. A variety of approaches including recent attempts to eliminate the suppressive effect of the dominant follicle have been used to reduce the unpredictability of the superovulatory response of cattle. The development of techniques such as transrectal ultrasonography, have enabled a re-evaluation of ovarian dynamics during superovulation of cattle. In addition, advances in reproductive hormone assays have increased knowledge of the mechanisms controlling follicular development, ovulation and corpus luteum function. This review focuses on the current understanding of factors affecting the superovulatory response of cattle. Also, abnormalities of ovulation and endocrine disorders that may occur during superovulation are reviewed.

Increasing the efficiency of suckled calf production using embryo transfer technology.

The data reviewed in this paper illustrate the benefits of increased output that can be obtained from suckler herds using embryo transfer technology. The technology can be used within breeding schemes to increase the rate of genetic progress for selected traits or to transfer embryos of superior genetic merit and, in the future, embryos of predetermined sex to beef cows. The success of the technology is dependent on the achievement of good pregnancy rates. Experience gained on commercial farms suggests that the main reason for poor success rates in some herds lies with the general level of management of such herds rather than with the reproductive technology itself. Much experience has been gained on the management of embryo transfer recipients and twin-bearing cows. In particular, the nutritional requirements of such animals during the early post partum period and during mid and late pregnancy, and the management of twin-bearing cows during the perinatal period, are discussed.

Embryo transfer technology and its use in enhancing dairy cattle breeding

Embryo transfer technology and its use in enhancing dairy cattle breeding

Use of MOET in Merino breeding programmes: a practical and economic appraisal

AbstractCommercial application of multiple ovulation and embryo transfer (MOET) technology will be subject to practical constraints and economic rationalism. This study examines use of MOET in its most profitable arena: to breed stud rams which will disseminate genetic improvement widely through multiplier studs to commercial flocks. A deterministic prediction is used to evaluate schemes based on an open nucleus MOET group within a Merino parent stud, taking account of genetic merit and inbreeding. Selection is based on clean fleece weight with an assumed heritability of 0·4. Embryos are collected at a rate equivalent to 3·45 live lambs per donor. Benefits of MOET were calculated from the discounted expressions of rams sold, and compared with the costs incurred.As the proportion of the flock born from MOET increases, the rate of genetic gain increases rapidly at first, but diminishing returns are observed. The costs ofMOET increase linearly with the number of lambs produced, so the optimum proportion ofMOET lambs is for practical purposes always less than 100%.Some use of MOET was profitable provided the stud sells sufficient stud rams each year. Sensitivity tests found that other parameters had only a small impact on the optimum level ofMOET. In general however, changes which increased the rate of genetic gain (heritability, flock size) or increased its value (wool price, lower discount rate) increased the optimum number ofMOET lambs.The results should provide guidelines to optimum investment in MOET for the wool industry. An across flock genetic evaluation scheme is probably necessary to motivate this investment.

Application of reproductive technology to buffaloes

This paper focuses on recent advances in the application of embryo transfer technologies to buffalo. The early recovery rate of 0.15 transferable embryos has now increased to 2.0, with altered superovulation protocols. Lower follicular population and poor follicular development, with adverse seasonal influences explain the lower ovulatory responses. Unovulated follicles at superovulation contribute high quantities of oestrogen, altering the uterine milieu. The birth of calves using in vitro fertilisation technology and frozen-thawed embryos and determination of embryonic sex using a Y-specific DNA probe, are recent milestones achieved using these technologies.

Embryo recovery from superovulated mouflons (Ovis gmelini musimon) and viability after transfer into domestic sheep

In this study multiple ovulation and embryo transfer (MOET) technology was tested as a method for increasing the number of offspring obtained from superovulated mouflons and then using Sardinian ewes as recipients. Two experiments were carried out over consecutive years. In Experiment 1, female mouflons received a standard superovulatory treatment during both breeding and anoestrous seasons. Sarda sheep, used as controls, received the same treatment. Mean superovulatory response (corpora lutea and large follicles) was higher in the domestic sheep than in the mouflons (4.8 vs. 10.1 and 4.2 vs. 8.8 in breeding and anoestrous seasons, respectively; P < 0.05). A high percentage of mouflons showed early luteal regression which negatively affected recovery rate (35% and 30% in mouflons vs. 69% and 71% in sheep) and the yield of embryos suitable for transfer (37% and 25% in mouflons vs 74% and 69% in sheep; P < 0.05). In Experiment 2, ten mouflons were treated by the same superovulatory protocol and divided into two groups. In the first (Group 5), embryos were recovered earlier by oviductal flushing and cultured in vitro with oviductal cells in CZB medium until the morula/blastocyst stage; in the second (Group 6), the usual embryo recovery time was followed. Recovery rate was higher in the former (89% vs. 31%; P < 0.01) than in the latter. After 4 days of culture, 53% of embryos reached compact morula or early blastocyst stage (16/30). Lambing rate was 57% for mouflon embryos transferred immediately and 56% for those cultured in vitro for 4 days; the lambing rate in the sheep control group was 71%. The length of gestation was longer in ewes carrying mouflons than in those carrying lambs (155 vs. 148 days).

Genetic parameters of purebred and crossbred Milking Criollos in tropical Mexico

AbstractRecords on total of 1746 calvings of principally Milking Criollos and their crosses were collected between 1972 and 1990 at the experiment station of the Mexican Association of Animal Production on the Gulf Coast of Mexico. Traits of interest were 305-day milk yield, days in lactation, number of services per lactation (raised to power 1/2), age at first calving and lifetime milk yield. Data were analysed by restricted maximum likelihood (REML) under an individual animal model based on 584 animals of which 146 were female ancestors and 35 were male ancestors. Heritabilities of 305-day milk and age at first calving were 0·17 and 0·07, respectively, but heritabilities of other traits were close to zero. Genetic trend in the Milking Criollos for 305-day milk was small and not significant (0·76 (s.e. 2·38) kg/year). Of crosses with Criollo sires, those involving Holstein and Canadienne breeding had highest 305-day and lifetime milk yields and those involving Brown Swiss and native Mexican (mostly Oaxaca) had lowest yields. Jersey crosses were intermediate for 305-day yield. The F1 Criollo × Jersey cross had highest lifetime yield, but backcrosses involving Jersey breeding were poor for lifetime milk. Additive breed effects for Jersey and Canadienne, relative to Milking Criollo, were 88 (s.e. 91) and 227 (s.e. 74) kg 305-day milk, respectively. Heterosis was 144 (s.e. 55) kg (11·6%) for 305-day milk, 16–4 (s.e. 9·6) (5·0%) for days in milk, −0·107 (s.e. 0–042) (7·7%) for number of services per lactation raised to power 1/2, −25·6 (s.e. 41·4) days (2•3%) for age at first calving and 1789 (s.e. 664) kg (60·0%) for lifetime milk. A plan was designed to develop a nucleus breeding scheme utilizing multiple ovulation and embryo transfer technology (MOET) for the genetic improvement of the Milking Criollo breed in Mexico.

Factors Associated With Dystocia Following Embryo Transfer to Heifers

Recent developments in cattle breeding technology have made the mass production of in vitro fertilised (IVF) embryos a realistic possibility. One use of this technology will be the production of “designer calves” for beef, from dairy and suckler cows. The IVF embryos used for this purpose are likely to have the genetic potential for high growth rates which may result in higher birth weights. If used incorrectly, this development in embryo transfer (ET) technology may increase the incidence of dystocia and therefore reduce the welfare of both cows and calves. A better understanding of the factors involved in dystocia would enable management action to be taken before ET and during pregnancy which would minimise dystocia and maximise welfare of both cow and calf.

A procedure for successful nonsurgical embryo transfer in swine

The current study was undertaken to develop a successful procedure for the nonsurgical transfer of pig embryos. A total of 663 embryos were surgically collected on Day 4 or 5 from 55 donors, of which 542 embryos of acceptable quality were nonsurgically transferred to 46 recipients. Nonsurgical recipient gilts were sedated 15 min prior to transfer with 20 mg im acepromazine maleate. A disposable insemination spirette with an attached 3-way stopcock was manipulated into the cervix of each gilt. Embryos were expelled from a tomcat catheter into the spirette, and 10 to 12 ml of Whitten's medium were used to flush embryos through the spirette into the reproductive tract. Sixteen (34.8%) recipient gilts did not return to estrus before Day 36, and 10 (21.7%) gilts farrowed with an average litter size of 4.3 +/- 0.7. Embryos were collected from an additional 20 donors and were surgically transferred to an additional 19 recipients. Surgical transfers conducted at the same time as the nonsurgical transfers resulted in 12 (63.2%) gilts farrowing and 7.1 +/- 0.6 pigs were born per litter. In conclusion, a procedure has been developed for nonsurgical transfer of swine embryos which simplifies the process of embryo transfer and which may increase the potential for utilization of embryo transfer technologies by swine producers.

Lesbian motherhood and genetic choices.

Rhonda, a physician, and Clara, a registered nurse, have been lovers for the past 7 years. Both women are in their 30s, in good health, and financially stable. Clara has contacted Dr. Robinson, a highly regarded obstetrician and geneticist, with an unusual request. Clara is seeking to become pregnant by means of in vitro fertilization (IVF) with an embryo transfer (ET) technology. She proposes being implanted with ova harvested from her partner, Rhonda, and fertilized in vitro with donor sperm from a local medical-school sperm bank. Dr. Robinson explains the relatively low success rate involved in IVF and ET techniques and suggests artificial insemination of Clara's own ova. Clara and Rhonda understand the low success rates but are undeterred. Their mutual goal is not merely to have a child but to share in the maternity of their children. What ethical issues are raised by the plan Clara and Rhonda propose? What are Dr. Robinson's ethical responsibilities with respect to the request by Clara and Rhonda?

Analysis of factors involved in the in vitro production of bovine embryos

Recent progress, briefly reviewed here, has led to utility of bovine in vitro oocyte maturation (IVM), in vitro fertilization (IVF), embryo culture and embryo transfer (ET) technologies in commercial and research endeavors. Undefined conditions incorporating selected serum, hormones and other active agents, and cellular constitutents or their contributions to support the in vitro production (IVP) of bovine embryos have enabled our achievement of IVF (cleavage) of 85% and blastocyst development of 40% of oocytes selected for IVM. Conditions for IVM have profound influence on subsequent events in IVP of embryos. Defined conditions for IVM coupled with semidefined conditions for IVF and cell-free embryo culture enable IVF of 74% and blastocyst development of 28% of immature oocytes selected for IVM. Efforts to understand a pronounced positive influence of LH during IVM on oocyte to blastocyst development in vitro led to recognition of variable hormonal effects on metabolism of bovine oocytes. Thus, LH markedly stimulates glycolysis and the tricarboxylic acid (TCA) cycle while TSH was found to increase glucose oxidation via the pentose cycle and FSH caused no change in metabolism of cumulus-enclosed oocytes (CEOs) in comparison to medium alone. Metabolic activities of CEOs is attributed primarily to the cumulus cells (CCs) but presence of the oocyte is necessary for hormonal responses observed. From ongoing research clues are anticipated to allow further understanding of important mechanisms and for development of improved methodologies for IVP of bovine embryos.

Current Status and Potential of Embryo Transfer and Reproductive Technology in Dairy Cattle

Significant use of embryo transfer in dairy cattle commenced with the introduction of nonsurgical embryo recovery in the mid-1970s and developed with the use of nonsurgical transfers in the late 1970s. Numbers of registered Holstein calves from embryo transfer doubled yearly through 1980, after which the rate of increase slowed; the total reached nearly 19,000 calves in 1990. However, the efficacy of superovulation procedures and commercial success rates of transferred fresh embryos have not improved the past 10 to 15 yr. Fertilization rates in superovulated donors remain low. Although embryo-splitting techniques were perfected in the early 1980s, they are not used widely. A practical, commercial embryo-sexing procedure remains unavailable. Recent significant improvement is apparent in the technology of ultrasound-guided oocyte collection and in vitro oocyte maturation, fertilization, and embryo culture. In the future, this technology may be used in conjunction with sperm separated by sex with a flow cytometer. Modest numbers of embryo clones have been produced in several commercial programs via nuclear transfer techniques. However, the efficiency of gene transfer experiments involving ova of cattle and other domestic species has been low. Recently, DNA probe technology has begun to provide genotype information for cattle and will ultimately be applied to embryos.

Future prospectives on animal biotechnology

Abstract Farm animal reproduction is entering the era of embryo engineering ‐ a part of the new biotechnology revolution that has been sweeping the nation during the early 1980s. This comes at a time when the $70 billion livestock industry is hard‐pressed for survival. Not since the commercial development of artificial insemination (AI) techniques in the 1950s has any new technical research development caused such a stir in the livestock community. The genetic impact of artificial insemination (AI) in the cattle industry these last 40 years cannot be questioned. Nearly three‐fourths of the dairy cattle in the United States are now being artificially inseminated. Also, commercial processing of bull semen has been and still is a major agribusiness success story, grossing millions of dollars annually. With the development of embryo transfer (ET) technology in the mid‐1970s, animal reproduction again entered a new age of technical advancement. It appears that AI and embryo methodology are just the beginning o...

Multiple superovulations in N'Dama heifers

Five N'Dama heifers were superovulated with follicle stimulating hormone (FSH-P or Folltropin) a total of six times each. The superovulations were carried out between ongoing experimental Trypanosoma congolense infections. Twenty-four (80%) of the 30 superovulations had a good ovarian response with 21 (70%) producing an average of 2.7 +/- 0.4 (mean +/- s.e.m.) embryos. The highest embryo production was achieved at the third and fourth superovulation, after which both the number of embryos and their quality declined. The overall pregnancy rate after transfer into Boran (Bos indicus) cow recipients was 50.9%. The uteri of the heifers increased considerably in size throughout the six superovulations which made it difficult to flush some of the animals after the third superovulation. Embryo transfer technology is a useful breeding tool in N'Dama heifers and multiple superovulations can be carried out with success.

An evaluation of the effects of thinning in dairy cows on animal production

Recent developments in in vitro fertilization and embryo transfer technology (Lu, et al, 1987) have facilitated the production of twin, continental cross calves from the dairy herd through non-surgical embryo implantation. However, the successful exploitation of this technology in practice requires information on the effects of embryo transfer and/or twinning on animal performance and how these effects may be influenced by feeding and management factors. The objectives of this study were to examine the effects of different management and feed regimes pre- and post-calving on the performance of single- and twin-bearing cows.