Embryo Transfer in Cattle Production and Its Principle and ...

Mebratu et al. Int. J. Phar. & Biomedi. Rese. (2020) 7(1), 40-54 ISSN: 2394 – 3726

Copyright © Jan.-Feb., 2020; IJPBR 40

Embryo Transfer in Cattle Production and Its Principle and Applications

Biruh Mebratu1, Haben Fesseha

2* and Eyob Goa

3

1College of Veterinary Medicine, Addis Ababa University, Addis Ababa, Ethiopia

2School of Veterinary Medicine, Wolaita Sodo University, P.O Box 138, Wolaita Sodo, Ethiopia

3College of Veterinary Medicine, Mekelle University, Mekelle, Ethiopia

*Corresponding Author E-mail: [email protected]

Received: 17.12.2019 | Revised: 22.01.2020 | Accepted: 28.01.2020

INTRODUCTION

In any livestock production system, efficient

reproductive performance and monitoring are

imperative for sustainability, especially for

milk, meat, draft, and replacement animals. In

recent times, there has been increasing

challenges for increasing productivity and

disease with altering climate. These targets,

thought to some extent, can be achieved by

conventional reproduction techniques.

Available online at www.ijpbr.net

DOI: http://dx.doi.org/10.18782/2394-3726.1083

ISSN: 2394 - 3726

Int. J. Phar. & Biomedi. Rese. (2020) 7(1), 40-54

ABSTRACT

The demand for animal products has grown several folds as a result of the increasing world

population. In this regard, livestock production has dramatically transformed allowing for

efficiency and improvement in productivity. For the past few years, significant improvements in

livestock productivity were achieved through the application of different biotechnologies,

followed by the extensive uptake of these new techniques. Embryo transfer is the process by

which an embryo is collected from the donor and transferred to another recipient to complete the

gestation period. The most recent advances are made in the areas of embryo transfer, in vitro

fertilization, artificial insemination, cloning, transgenesis and genomics. While some of these

applications are still under continues research scale ups. Bovine embryo transfer technology

involves the selection and management of donor and recipient animals and the collection and

transfer of embryo within a narrow window of time following oestrus. The application of this

method is numerous in cattle production to amplify reproductive rates of valuable females,

genetic improvement, twining, disease control, planned mating, increased farm income, and

others. Because of low reproductive rates and long generation intervals, embryo transfer is

especially useful in this species. However, embryo transfer is still not widely used despite its

potential benefit. The greatest challenges often associated with this in the developing world are

lack of adequate technology due to high cost and technological skills associated with the entire

process. Although this technology is not commercially available in developing countries, ET

technology could provide opportunities for the conservation and the development of minor

breeds.

Keywords: Application, Cattle, Donor, Embryo transfer, Livestock production, Recipient

ReviewArticle

Cite this article: Mebratu, B., Fesseha, H., & Eyob Goa, E. (2020). Embryo Transfer in Cattle Production

and Its Principle and Applications, Int. J. Phar. & Biomedi. Rese. 7(1), 40-54. doi:

http://dx.doi.org/10.18782/2394-3726.1083



Advent and use of modern reproductive

technologies have opened many avenues to

study, treat and manipulate the reproductive

phenomenon of both in vitro and in vivo to

improve reproductive performance in various

domestic species of livestock (Choudhary et

al., 2016).

Embryo transfer (ET) is a process by

which an embryo is collected from a donor

female and then transferred into a recipient

female where the embryo completes its

development (Stroud, 2012). ET is profitable

for producers of registered pure breed animals.

By far the most common use of embryo

transfer in animal production programs is the

proliferation of so called desirable phenotypes

and production of artificial inseminated (AI)

bulls through planned matting. Many breeders

have identified individual females whose

offspring are most saleable and used them

exclusively in embryo transfer (Fufa et al.,

2016). Selection criteria for the donor animals

are very likely to differ depending on the

reason for doing ET. Selection should be based

on three criteria: genetic superiority,

reproductive ability and market value of the

progeny (Fufa et al., 2016).

From historical perspective on assisted

reproduction, the first successful transfer of

mammalian embryos was performed by Walter

Heape in 1890. The first successful embryo

transfers in cattle were reported by Umbaugh

in 1949. He produced four pregnancies from

the transfer of cattle embryos, but all the

recipients aborted before the pregnancies

reached full term. In 1951, the first embryo

transfer calf was born following the surgical

transfer of an abattoir-derived day-5 embryo

(Mapletoft, 2013).

Developing countries have nearly two

thirds of the world livestock population, but

produce only about a quarter to a third of the

world’s meat, and a fifth of the milk (Rege,

2009). New technologies can help to achieve

high productivity, but need to be transferred to

producers to cause impact (Ehui & Shapiro,

2009; Yang and Honaramooz, 2010).

Naturally, a cow produces about 8 to 10 calves

in her lifetime. But with ET, it is possible to

get 32 embryos per cow per year compared to

the conventional method of breeding where the

farmer has to wait for twelve months for a calf

that could be either male or female (Glenn,

2004; Steel & Hasler 2004; Muchemi, 2011).

This review was organized to review the

principles, applications and the benefit of

embryo transfer in cattle productivity and

production.

2. GENERAL PRINCIPLES OF EMBRYO

TRANSFER

By collecting embryos from genetically elite

females and transferring the harvested

embryos into females of lesser genetic merit, it

is possible to produce more calves from

genetically superior females and fewer calves

from genetically less valuable females

(Youngs, 2007). Therefore, to achieve this

goal the bovine female ovulates multiple,

matured and viable oocytes, which are capable

of being fertilized in-vivo, and which can then

continue to develop into embryos (Smith,

2015).

Embryo collection is undertaken on

day 7 of the oestrous cycle (day 0 = day of

oestrus). Although early embryo transfer

techniques utilized surgical approaches to

embryo collection, now all commercial

embryo collections are non-surgical

procedures requiring trans-cervical

catheterization of the uterine horns (Smith,

2015).

2.1. Selection and Management of Donor

and Recipient Cow

2.1.1. Selection and management of donor cow

and sires

Selection of superior genetic or phenotypic

animals has been the basis of the donor

selection since ET`s inception (Philips and

Jahike, 2016). Genetic superiority animals that

contribute to the genetic objectives of the

programme and likelihood of producing large

numbers of usable embryos are the two broad

criteria for selecting donor cows for most

embryo transfer programmes (Thibier, 2006).

In fact, selecting the male is usually

more important than selecting the donor

female because males will normally be bred to

many females and can be selected more



accurately than females. Likewise, it is

necessary to select fertile bulls and fertile

semen which makes it especially important to

use high quality semen (David & Hamilton,

2016). Donors are located either on the farm

under production conditions or at an embryo

transfer centre, frequently under intensive

management. Keeping donors on the farm is

usually the less expensive alternative (George

et al., 2005).

2.1.2. Selection and management of recipient

One of the most important yet

underappreciated aspects of successful ET

program is the recipient. Cows that are

reproductively sound, that exhibit calving

ease, and that have good milking and

mothering ability are recipient prospects. They

must be on a proper plane of nutrition. These

cows also must be on a sound herd health

program (Selk, 2010).

Proper recipient herd management is

critical to ET success. Management of this

herd requires fundamental understanding of

the recipient selection, nutrition, estrus

synchronization, disease management, and

marketing (Schmidt, 2010). Personnel at the

farm must have certain skills and, above all, be

extremely conscientious (George et al., 2005).

2.2. Synchronization of Recipient

To maximize embryo survival in the recipient

female following transfer, conditions in the

recipient reproductive tract should closely

resemble those in the donor. This requires

synchronization of the estrous cycles between

the donor and the recipients, optimally within

one day of each other. Synchronization of the

recipients can be done in a similar manner and

at the same working time as the donor cows

(Galina & Orihuela, 2007).

Recipients synchronized with

prostaglandin F2α (PGF2α) must be treated 12

to 24 hours before donor cows because

PGF2α-induced estrus will occur in recipients

in 60 to 72 hours (Genzebu, 2015) and in super

ovulated donors in 36 to 48 hours (Baruselli

and Moreno, 2002). Synchronizing products

are more effective on recipient females that are

already cycling (Berber et al., 2002). The

synchronization protocol used is shown in

Table 1.

Table 1: Recipient protocol synchronises

Days in sequence Time of the day Activity

1 8.00-10.00 AM Inject 20ml multivitamine

7 8.00-10.00AM Insert CIDR device+2 ml ciderol

12 8.00-10.00 AM Inject Estrumate

14 8.00-10.00 AM Inject Estrumate

15 8.00-10.00 AM Remove CIDR device

16 8.00-10.00 AM Observe heat

24 8.00AM-5.00 PM Transfer

CIDR= (Controlled Internal Drug Release device)

Source: (Ongubo et al., 2015)

2.3. Superovulation of Donor

Superovulation refers to the release of many

oocytes (eggs) during a single estrus period

(Mapletoft, 2003). Once the donor cow is the

selected, the first step is to super ovulate or

produce multiple ova (eggs) for simultaneous

fertilization and subsequent collection.

Initially, the donor female is treated with

gonadotropin hormone called follicle

stimulating hormone (FSH). This hormone is

administered twice daily for four days in the

range of eight to fourteen days while a

functional CL is on the ovary. A PGF2α

injection given on the fourth day of the

treatment schedule will cause CL regression

and estrus to occur approximately 48 hours

later. As the result of treatment multiple

follicles should be developed on the ovaries of

the donor. Multiple numbers of eggs will be

released at estrus, one from each follicle

(Stephen & Blizinger, 2007).



Fig. 1: Superovulation schedule using CIDRs and GnRH. PGF2α, prostaglandin

Source: (Philipes and Jhanke, 2016)

2.4. General Procedure

The actual embryo transfer process is similar

to the method used for artificial insemination,

except that the transfer gun is passed well up

the uterine horn ipsilateral to the CL (George

et al., 2005). The donor may be inseminated

naturally or artificially and embryos will be

collected non-surgically six to eight days after

breeding. Following collection, embryos must

be identified, evaluated and maintained in a

suitable medium prior to transfer. At this

point, they may also be subjected to

manipulations, such as splitting and sexing,

and may be cooled or frozen for longer periods

of storage (Hasler, 2003).

2.5. In vivo and In vitro Fertilization

2.5.1.In vivo fertilization

During normal in vivo embryonic

development, blastomeres go through a series

of cleavage divisions. The ovum, after

fertilization, divides and develops into a 2-cell

embryo, the 2-cell develops into a 4-cell, the

4-cell into an 8-cell, etc. when the blastomeres

appear like a cluster of a grapes and individual

blastomeres can`t be differentiated, this stage

of embryonic development is known as the

morula stage. As the embryo further develops,

it prepares to undergo its first differentiation

event known as blastulation. Just prior to this

differentiation event, cells of the morula

“compact” and are allocated to the “inside”

and “outside” parts of the embryo (Jahnke et

al., 2014).

2.5.2. In vitro fertilization

Although each ovary contains

hundreds of thousands of oocytes at birth,

most are lost through atresia. This tremendous

loss of genetic material could be reduced by

harvesting oocytes from the ovary and using in

vitro production (IVP) techniques. Bovine IVP

is now a well-established and reasonably

efficient procedure. Moreover, ovum pick up

(OPU) at frequent intervals, in combination

with in vitro fertilization (IVF), has proved its

worth in improving or increasing the yield of

embryos from designated donors (Mapletof &

Hasler, 2005).

This procedure usually comprises four

separate steps in vitro: oocyte maturation,

capacitation of sperm, fertilization, and culture

of embryos until they can be frozen or

transferred to the uterus. The actual IVF step is

the easiest of the four, but success requires that

the other steps work well. Oocyte maturation,

capacitation, and culture of embryos can all be

done in vivo, but as the number of in vivo steps

increases, the practicality decreases greatly

(George et al., 2005).

2.6. Embryo Recovery

In most cases, embryos are recovered six to

eight days after the beginning of oestrus (day

0). Embryos can be recovered non-surgically

as early as four days after oestrus from some

cows, but prior to day 6 recovery rates are

lower than on days 6 to 8. Embryos can also

be recovered on days 9 to 14 after oestrus;



however, they hatch from the zona pellucida

on day 9 or 10, making them more difficult to

identify and isolate and more susceptible to

infection. After day 13, embryos elongate

dramatically and are sometimes damaged

during recovery or become entangled with

each other. Procedures for cryopreservation

and bisection have been optimized for day 6–8

embryos, which is another reason for choosing

this time (George et al., 2005).

Fig. 2: Diagram of the embryo flushing and recovery procedure

Source: (Selk, 2010).

2.7. Embryo Handling, Evaluation and

Storage

2.7.1. Embryo handling

Embryos are normally held in the same or a

similar medium to that in which they were

collected (IVIS, 2006) as shown in Table 2.

Careful handling of embryos between

collection and transfer is necessary to prevent

the transmission of pathogens. The use of

aseptic techniques, sterile solutions, and sterile

equipment is essential (Peregrino et al., 2000).

Table 2: Recommended culture condition for bovine embryo

PH 7.2-7.6

Osmolality 270-310 mOs M/kg

Humidity 100 %

Temperature Room temperature(15-25oC ) or 37

oC in incubator

Buffer Phosphate or bicarbonate ion (later must be maintained under 5% CO2 atmosphere)

Source: (George et al., 2008).

2.7.2. Embryo evaluation

Embryos are classified and evaluated by

morphological examination at 50 to 100 X

magnification according to the Manual of

the International Embryo Transfer Society

(IETS) (Givens et al., 2010). The overall

diameter of the bovine embryo is 150 to

190 µm, including a zona pellucida

thickness of 12 to 15 mm. The overall

diameter of the embryo remains virtually

unchanged from the one cell stage until

blastocyst stage (Bekele et al., 2016).

Generally the major criteria for

quality evaluation include; regularity of

shape of the embryo, compactness of the

blastomeres (the dividing cells within the

boundaries of the embryo), variation in

cell size, color and texture of the

cytoplasm (the fluid within the cell wall),

overall diameter of the embryo, presence

of extruded cells, thickness and regularity

of the zona pellucida (the protective layer

of protein and polysaccharides around the

single celled embryo) and presence of



vesicles (small bubble like structures in the cytoplasm) (Bekele et al., 2016).

Fig. 3: Illustration of a blastocyst stage bovine embryo.

Source: (Jahnke et al., 2014)

2.7.3. Embryo storage

Procedures such as ET, IVF, sex

determination, and cloning depend on

maintaining the viability of embryos for hours

to days outside of the reproductive tract. For

many applications, the storage system must

not only maintain the viability of the embryo,

but must also support continued development

(Sauvé, 2002).

2.8. Transfer of Bovine Embryo

Transfer of embryos in the cow will result in a

high pregnancy rate providing the preceding

estrus in the donor and recipient occurred

within 24 h of each other (Mapletoft, 2006;

Smith, 2015). The successful utilization of

both surgical and non-surgical embryo transfer

in animal breeding programs represents a

significant new approach for animal breeders

(Baruselli et al., 2006).

George et al., (2005) suggested that,

both surgical and non-surgical methods of

embryo transfer can be made to work well.

Under most circumstances, non-surgical

transfer is greatly preferred, although surgical

transfer can be done quite rapidly, even in

rather primitive circumstances as described in

Table 3.

Table 3: Comparison of surgical and nonsurgical methods for recovery of embryo

Method of recovery

End point Surgical Nonsurgical

Anesthesia General Epidural

Fasting Required Non required

Ability to recovery embryos at any stage Excellent Limited

Ability to accurately assess number of ovulation Excellent Poor

Risk of accurate complication to donor Definite possibility Virtually nil

Risk to future reproductive performance of donor Yes Probably none

Embryos recovery rate Excellent Good

Source: (Betteridge, 2003)

3. APPLICATIONS OF EMBRYO

TRANSFER IN CATTLE PRODUCTION

The widespread use of embryo transfer

technology in animal breeding schemes is

relatively recent. Genetic engineering and

related new technologies will only increase its

utilization (Mapletof, 2006). Common uses of

embryo transfer technology in cattle



production are as follows (Table 4) (Lucero, 2015).

Table 4: Contribution of embryo transfer in animal production

Contribution Role in animal production

Rapid gene pool expansion Expand gene pools of rare breeds or in controlled geographical

region.

Increased selection intensity

in females

Approximately double selection intensity among offspring of

selected dams in beef cattle

Increased twining rate Increased number of calves produced per gestation.

Facilitate seed stock transport To aid transport of diploid genome of frozen or cultured embryos

with reduced disease hazard from country to country.

Utilize prepubrtal cocytes and

in vitro fertilization

Reduce generation time and utilize genetic potential of more oocytes

present in bovine ovary.

Gene–environment

interaction studies

Facilitate research into maternal-fetal interaction with reference to

reproductive rate, pharmacological and disease states

Source: (Can, 2018)

3.1. Genetic Improvement

Genetic progress has generally been

considered to be slower with embryo transfer

than with conventional artificial insemination,

especially on a national herd basis. However,

with increased selection intensity and

shortened generation intervals, i.e.,

transferring female offspring, genetic gain can

be made on a within-herd basis (Bekel et al.,

2016). This has resulted in the term MOET

(multiple ovulation and embryo transfer)

(Thomas, 2007).

In several countries around the world

nucleus herds are now being developed and

heifer offspring are being subjected to

"Juvenile MOET", while male offspring are

being selected for the next generation of AI

bulls. In this way, it has been estimated that

genetic gains can be doubled. On the other

hand, it has been estimated that the production

of about six offspring per donor cow could

double selection intensity and the rate of

response to genetic selection for traits such as

growth that can be measured in both sexes

(Mapletof, 2006).

ET is now commonly used to produce

AI sires from proven donor cows and bulls in

AI service. In addition, new genomic

techniques are being used increasingly to

select embryo donors; genomic analysis has

become essential for the selection of bull dams

to be used in embryo transfer (Seidel, 2010).

Although economics would not at this time

support the use of embryo transfer techniques

for anything but seed stock production, the

commercial cattle industry can benefit by the

use of bulls produced through well-designed

MOET programs (Bekel et al., 2016).

3.2. Planned Mating

By far the most common use of embryo

transfer in animal production programs is the

proliferation of so-called desirable phenotypes.

As AI has permitted the widespread

dissemination of a male's genetic potential,

embryo transfer provides the opportunity to

disseminate the genetics of proven, elite

females. ET also permits the development of

herds of genetically valuable females

(Mapletof, 2006).

Many breeders have identified

individual females whose offspring are most

saleable and used them exclusively in ET.

Embryo transfer has also been used to rapidly

expand a limited gene pool. The production of

AI bulls through embryo transfer is the most

common application of planned mating (Fufa

et al., 2016).

3.3. Disease Control

Even though ET is better and efficient

technique, the risk of transmitting genetic

disease the same as that involved in natural

mating or AI so, wise selection of dams and

sires is mandatory, no matter how cattle are

propagated. There is no increased incidence of

abnormal offspring due to these procedures.

With this technology, however, there may be



greater temptation to amplify reproduction of

cows with a very high market, some kinds of

infertility with a genetic basis can be

circumvented and because the sale of the

offspring can be very profitable (George et al.,

2005).

Embryo transfer procedures can be

used to control large-scale transmission of

genetic diseases such as syndactyly by

screening young bulls for undesirable

recessive Mendelian characteristics before

semen is distributed for AI. Also embryos

from parents with abnormal karyotypes can be

biopsied and karyotyped, and only the normal

ones transferred (George et al., 2005). Risk of

infectious disease transmission is less by IVP

embryos, providing embryo handling

procedures were done correctly (Stringfellow

et al., 2004). In fact, the IETS has categorized

disease agents based on the risk of

transmission by a bovine embryo (Stringfellow

& Givens, 2000; Mapletoft & Hasler, 2005).

Category 1 diseases, for which

sufficient evidence has accrued to show that

the risk of transmission is negligible, provided

that embryos are properly handled between

collection and transfer. This includes

inspection of the zona pellucida at >50X

magnification and washing/trypsin treatment

procedures. Category 1 diseases include

Enzootic bovine leucosis, Foot and mouth

disease, Bluetongue, Brucella abortus,

Infectious bovine rhinotracheitis /IBR/,

Haemophils somnus, Bovine genital

campylobacteriosis, Trichomoniasis,

Leptospira, Chlamydia, Genital Mycoplasma

and Bovine spongioform encephalopathy can

be transmitted through ET. Consequently, it

has been suggested that ET be used to salvage

genetics in the face of a disease outbreak,

which could be a useful alternative in

establishing disease-free herds (Wrathall et al.,

2004; Mapletoft, 2006).

3.4. Circumvent Infertility

It is possible to obtain offspring from

genetically valuable cows that have become

infertile due to injury, disease, or age by

means of superovulation and ET. Infertile

heifers and cows with genetically caused

subfertility should not be propagated (George

et al., 2005). Although success rates are low, it

is possible to recover oocytes from genetically

valuable, moribund cows, fertilize them in

vitro, transfer them, and obtain offspring as

listed in Table 5 (Marahall et al., 2002).

Table 5: Therapy for various types of infertility based on embryo transfer procedures

Cause of infertility Procedure

Uterine infection

In cases of persistent pyometra in which volumes of fluid and debris

build up in the uterus, it is often efficacious to flush the uterus with 0.9

percent NaCl until the recovered fluid is clear, and then to administer

PGF2α. Penicillin or oxytetracycline may be infused for three to four

days but, if not done carefully, can do more harm than good. Normal

embryo transfer procedures can be followed after the next oestrus. In

cases of subclinical or recurrent endometritis, repeated superovulation

and ET may result in the “rescue” of viable embryos from the toxic

environment to develop in the healthy uterus of the recipient.

Repeat breeder

Heifers in this category should not be propagated. With normally

cycling, parous cows one should try at least three times to recover a

single ovum to diagnose if there is ovulation, and if the ovum has been

fertilized. It may be helpful to use raw semen. If a morphologically

normal embryo at the expected stage of development is recovered,

consider progesterone therapy during gestation.

Aged repeat breeder

Problem likely due to “worn-out” uterus; normal superovulatory

treatment and transfer of embryos to uterus of younger recipient is

often effective.

Cystic ovarian disease Often superovulatory treatments based on the insertion and removal of

a progestin implant rather than on PGF2α injection are effective. If the



cystic ovarian condition appears to be hereditary, no propagation

should be attempted.

Adhesions of ovaries or

blocked oviducts

Superovulation increases the chances that at least a few ova will be

picked up if there are adhesions. A combination of superovulation with

surgical recovery or laparoscopy helps to diagnose the cause of the

infertility and can result in recovery of viable embryos for transfer.

Some conditions can be corrected surgically (e.g., flushing plugs of

debris from the oviduct), although relieving adhesions is rarely of

lasting benefit

Chronic abortion Recovery of the embryo before the abortion-causing condition is

active can often circumvent the resulting infertility.

Source: (George et al., 2005)

3.5. Twinning in Cattle

Cattle twinning for beef production could offer

impressive economic advantages where

nutrition is not a limiting factor and intensive

management is possible. Since about 70

percent of nutrients consumed by dams are for

body maintenance and the other 30 percent go

to producing the foetus and milk to feed the

calf, it should theoretically be possible to

produce twice as many calves with only 30

percent more nutrients if cattle had twins.

Probably a 60 percent increase in feed costs is

more realistic due to higher morbidity and

mortality and slower growth rates with twins.

In practice, one would probably decrease cow

numbers and increase calf numbers (due to

twins) so that the amount of nutrients used per

farm would remain constant (George et al.,

2005).

3.6. Embryo Transfer as Part of other

Biotechnology

As mentioned by George et al., (2005),

detection of carriers of undesirable Mendelian

recessive traits via ET is very effective for

both cows and bulls. For certain traits like

syndactyly and dwarfism, there is a shortage of

homozygous, fertile females to use as mates

for suspected carrier bulls. Embryo transfer is

an obvious means of amplifying gamete (and

embryo) production of such females so that

bulls can be tested for carrier status.

ET also provides a method of testing

daughters of carrier bulls to determine which

half does not have the deleterious allele. Since

at least seven defect-free calves are required to

be 99 percent certain that a given animal is not

a carrier, it would normally take longer than

the average reproductive lifespan of a cow to

test this; furthermore, all the calves produced

during the test would be carriers because of

using semen from a double recessive bull.

With superovulation and ET, one or two

courses of superovulation will provide enough

embryos to test most cows; moreover,

recipients can be twinned and the fetuses

examined at about two months of gestation to

diagnose many of these defects. Thus, with

embryo transfer a quick answer is possible to a

problem that is otherwise intractable (George

et al., 2005).

Exploitation of other technologies that require

manipulating the oocyte or embryo in vitro

depends on good embryo transfer techniques

for success. Such technologies include IVF,

sexing, production of transgenic animals,

bisection of embryos and cloning by nuclear

transplantation (George et al., 2005).

4. ECONOMIC IMPORTANCE OF

EMBRYO TRANSFER

In approximately for 40 years, commercial

embryo transfer in cattle has become a well-

established industry with more than 500,000

embryos being transferred on an annual basis

through the world (Mapletoft, 2012). ET is

being used for genetic improvement,

especially in the industry and most semen used

today comes from bulls produced ET (Fufa et

al., 2016).

4.1. Cost of Embryo Transfer

Costs of embryo transfer vary greatly from

country to country, and within countries,

depending on a variety of factors. However,

two generalizations can be made. First, no

matter how it is done, embryo transfer

programmes are relatively expensive. The

costs of the actual ET services or technology



may be quite low; however, labor and feed

costs averaged over the number of calves

produced are high since normal, healthy cows

or heifers are kept out of production in order to

be available as recipients. Second, costs per

calf are lowest when success rates are high,

because costs are spread over more calves.

Costs will be listed assuming that embryo

recovery and transfer services are purchased.

In many cases, these services will be provided

by a government, a cooperative or the

company owning the cattle, when the costs

should be determined in a different way; they

will still be real costs, nonetheless (George et

al., 2005).

4.2. Import and Export

The desire to improve herds of cattle, to

increase variation in the gene pool, and to

introduce new breeds, has motivated the

importation/exportation of breeding stock. In

the past, trade has been primarily either in

young animals with outstanding pedigrees or

semen. Animals have the advantage of being

100 percent of the desired new genotype and

are usually of breeding age so that impact on

the herd is immediate. The disadvantages are

that costs, especially for transportation, are

very high and that there is a high morbidity

rate if the new environment is markedly

different in management, climate, or endemic

pathogens. Moreover, if cows are imported,

the genetic influence on the general population

is limited until their bull calves reach breeding

age (George et al., 2005).

The intercontinental transport of live

animals also costs thousands of dollars,

whereas an entire herd can be transported, in

the form of frozen embryos, for less than the

price of a single plane fare (Mapletof, 2013).

Additional benefits of frozen embryos for the

international movement of animal genetics

compared to live animals includes reduced risk

of disease transmission, reduced quarantine

costs, a wider genetic base from which to

select, the retention of the original genetics

within the exporting country, and adaptation

(Table 6) (Stroud, 2012).

Table 6: Comparison of importing germplasm as postparturient animals, as semen or as embryos

Advantage Disadvantage

Postparturient animals

Animals productive quickly Expensive

Animals often succumb to disease

Chance of introducing exotic disease

Complex transportation logistics

Limited immediate genetic influence if females are

imported

Semen

Inexpensive Need to grade up to get pure-bred animals

Low risk of disease transmission Need for Al technology

Hybrid vigour, F1 and F2 Long wait until animals productive

Simple transportation logistics

Passive immunity from native dam

Embryo

Very low risk of disease transmission Need for ET technology

Costs may be lower than animals Long wait until animals productive

Simple transportation logistics

Passive immunity from native dam

Source: (George et al., 2005)

4.3. Farm Income Increased

Reproduction can have a multitude of impacts

on a farm, from altering culling policies,

increasing retention of better replacements,

moving primiparous cows into a more

productive the second lactation and improving

milk production. Because production accounts

for more than 88% of the gross income of a

dairy farm (Santos et al., 2010) it is no

surprise that most attention paid to



improvement in reproduction evolve around

altering milk production during the productive

life of cows.

In most cases, altering milk production has to

be considered per day of calving interval, as

improvements in reproduction increase the

time a cow spends in the dry period, which is

considered a nonproductive stage of the

lactation cycle. Improving reproduction often

times results in greater availability of

replacement animals, which increases herd

turnover (Ribeiro et al., 2012).

5. APPLICATION OF BOVINE EMBRYO

TRANSFER IN DEVELOPING

COUNTRY

Livestock production is one of the fastest

growing agricultural subsectors in developing

countries, where it accounts for more than a

third of agricultural gross domestic product

(GDP) (FAO, 2006). Livestock production is

expected to grow tremendously in line with the

projected demand for animal products.

Therefore, the methods of livestock production

must change to allow for efficiency and

improvement in productivity (Kahi & Rewe,

2008).

Biotechnology is important if the

world is to respond to the pressure to produce

more food from animals for the ever-growing

human population. In general, biotechnology

in livestock production can be categorized as

the biological, chemical and physical

techniques that influence animal health

(survival), nutrition, breeding and

reproduction. These techniques have been

applied mostly in developed countries but their

application in Africa is minimal due to reasons

related to economic growth such as poor

infrastructure, technical and educational

capacity (Kahi & Rewe, 2008).

Quantitative information on the

current status of use of animal biotechnologies

in developing countries is lacking, except the

use of some assisted reproductive

biotechnologies such as AI, ET and molecular

markers (FAO, 2010). Artificial insemination

and embryo transfer are probably the most

popular methods that have been adopted in

developed and developing livestock industries.

Embryos produced in vitro have led to

successful births of buffalo and cattle calves in

developing countries (Madan, 2005). The

animal species in which the technology has

been applied are cattle, buffaloes, horses and

goats (FAO, 2007). ET is limited to highly

commercialized livestock production systems

and more popular with cattle than any other

species (Robinson & McEvoy, 1993).

After artificial insemination and oestrus

synchronization, embryo transfer is the third

most commonly used biotechnology (Cowan,

2010). ET from one mother to a surrogate

mother makes it possible to produce several

livestock progenies from a superior female.

However, ET is still not widely used despite

its potential benefits. An evaluation of country

report (FAO, 2007) shows that only five of the

African countries providing information (Cote

d`Ivore, Kenya, Madagascar, Zambia and

Zimbabwe) use ET technology, all on a very

limited scale. The use of ET also been

independently reported in South Africa

(Greyling et al., 2002).

5.1. Challenges of Embryo Transfer

In Africa, livestock are still being reared in

natural pastures and environments that are

acceptable by most consumers worldwide. The

potential for Africa in the international

livestock industry is therefore promising as

demonstrated by the encouraging

developments in stable countries in the south

(Republic of South Africa), east (Kenya) and

west (Ghana) (Kahi & Rewe, 2008). The

utilization of embryo transfer in Africa is

mainly an issue of cost benefit analysis and

infrastructure. The majorities of farmers are

smallholder and have found that returns do not

measure to the investment in ET technology

considering that ET involves cryopreservation

of embryos as well as in-vitro maturation,

fertilization and culture, which are expensive.

The transport systems and technological

capacity is still too poor in some countries of

Africa to sustain the spread of reproductive

biotechnologies (Kahi & Rewe, 2008).

The major constraints of animal

biotechnology in developing countries

includes: insufficient access to land and other



productive resources, unfavorable terms of

trade for food products, especially for animal

products, lack of database on livestock and

animal owners , uniqueness of animal breeds,

lack of trained scientists, technicians and field-

workers, absence of coordination between

industry, universities and institution for

technology transfer, expensive technology to

be purchased from developed world, high cost

of technological inputs, poor bio-safety

measures, negligible investment in animal

biotechnology, lack of clear policy and

commitment from the government, disregards

for indigenous knowledge and local

agricultural resources management (Seidel &

Seidel, 1992).

In addition, factors such as lack of

political stability and poor conditions of the

human population like poverty, malnutrition,

disease, poor hygiene and unemployment are

also the constraints and limitation of

biotechnology in animal production in

developing countries (Madan, 2003).

5.2. Embryo Transfer in Ethiopia

The first successful embryo transfer in

Ethiopia, resulted in the birth of a Holstein-

Jersey calf at the Adami Tulu Animal

Research Center in the beginning of May,

2010 and five more calves had born. In April

2010, eighty frozen embryos that were

imported the previous August were implanted

in the native cows (Madan, 2003).

Ethiopia is a home of diverse

indigenous cattle breeds and Boran cattle are

one of them. However, effort made so far to

increase the productivity on Boran cattle in

Ethiopia was fully based on crossing with

exotic breeds either through AI or natural

breeding. As a result, crossbreeding of Boran

with Holstein has resulted in improved growth,

milk production and reproductive

performance, and these traits exhibited an

increasing trend with increasing exotic

inheritance level (Demeke et al., 2000; Haile

et al., 2009).

The Boran is a Bos indicus cattle

breed, and under ideal management conditions

it is generally accepted that Bos indicus cattle

are less fertile and have lower levels of milk

production than Bos taurus breeds. However,

Bos indicus breeds typically are better adapted

to harsh environmental conditions and

therefore are more likely to reproduce

successfully (Degefa et al., 2016).

Boran cattle breed is also the only

indigenous breed exposed to assisted

reproductive technology other than AI in the

process of breed improvement, even though

reproductive technologies are mostly

developed for Bos taurus breeds. Boran breeds

showed a relatively better potential for

application of embryo technology in terms of

ovarian follicular growth, superovulatory

response, and embryo production (Degefa,

2016).

6. CONCLUSION AND

RECOMMENDATIONS Embryo transfer in cattle has grown into a

mature international business with high

success rates and it becomes a well-established

industry. Its impact is large because of the

quality on animals being produced. Embryo

transfer is now being used for real genetic gain

and most semen used today comes from bulls

that have been produced by embryo transfer. It

also offers other important contribution to

increase numbers of offspring by production of

twines. Although embryo transfer is generally

costly in both developed and developing

countries, it is profitable. However, embryo

transfer is still not widely used despite its

potentials. In developing countries such as

Ethiopia, could only make use of the

technology in teaching and research purpose

due to absence of the necessary facilities and

infrastructure. Since the technology upgrades

and maximizes the genetic potential and hence

the productivity of animals, it is best if used in

our local breeds. In conclusion, Coordination

should be existing between industries,

universities and institutions to create well

trained technician for embryo transfer

technology. Ina ddition, awareness should be

created in the community and companies about

the profitability of embryo transfer.

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