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B124 Embryo Transfers
Name __________________________________ Date _______________
Introduction
Define Embryo transfer:
The art of bovine embryo transfer (ET) is an ever changing science that involves three major events.
1. It begins with selection, ______________________, and ____________________ (A.I.) of the donor animal.
2. Next, the embryos are recovered from the donor through either surgical or nonsurgical means, evaluated, and then ___________________ or ____________________________.
3. Lastly, the recipient animals are _______________________________ and receive the embryos through surgical or nonsurgical techniques.
Objectives
This lesson will briefly discuss the history and benefits of embryo transfer.
We will also focus on the details of ET and discuss the various pros and cons of the surgical and nonsurgical approaches.
History
The first successful embryo transfer was performed in _______________ using ____________________ embryos.
The first bovine embryo was recovered by Hartman, Lewis, Miller and Swett in ___________ at the Carnegie Laboratory of Embryology in Baltimore.
In the ________________, embryo transfer technology in cattle expanded with the first successful transfer performed by Umbaugh and the first calf born through a joint effort by the USDA and the University of Wisconsin.
Until the 1970's progress was slow, with many ideas ending in failure.
As ___________________________ methods advanced through the efforts of Elsden, Hasler, Seidel and others, the commercial use of embryo transfer exploded.
In ___________________, over __________________ ET calves were registered in the United States.
Why Consider Embryo Transfer In Cattle?
The reproductive potential of each normal newborn calf is enormous. There are an estimated ___________________________ potential “eggs” or ova in the female and countless _________________________ of sperm produced by each male.
By natural breeding, only a fraction of the reproductive potential of an outstanding individual could be realized.
The average herd bull will sire ______ to _______ calves per year and the average cow will have _______ calf per year.
With artificial insemination, it is possible to exploit the vast numbers of sperm produced by a genetically superior bull.
However, the reproductive potential of the female has been largely un-utilized.
She will produce an average of _______________________ calves in her entire lifetime under normal management programs.
Like artificial insemination has done for the bull, embryo transfer is a technique that can greatly increase the number of offspring that a genetically important cow can produce.
Each of these offspring would potentially carry the superior traits of the mother, such as increased weight gain, increased size, or even increased milk production.
Embryo transfer also eliminates the stress of _____________________________ on a desirable animal, thereby increasing her reproductive life span.
______________________________, salvage of reproductive function, and potential twinning are a few of the other benefits of embryo transfer.
Selecting a Donor
Selection of a proper donor is essential to the success of the embryo transfer program. A potential donor can be selected based on the following criteria:
Possesses ________________________________ desired in the herd.
Must be at least _______ months of age.
Has __________________________, normal estrous cycles.
Has not had greater than two services per ____________________________ .
Has not had previous conformational, parturition, or reproductive problems.
Must be ________________________________.
Superovulation
Superovulation occurs when supplemental _________________________ are given to stimulate the production of eggs.
Instead of producing a single egg during estrus the animal will produce many ________ eggs during estrus.
Superovulation treatments often utilize 5-6 mg of ____________________________ (FSH) given twice daily for 4 days.
This dose is gradually decreased each day.
For example 6mg A.M. and P.M. (day 1), then 4mg A.M. and P.M. (day 2), 2mg A.M. and P.M. (day 3), 2mg A.M. then administer a dose of ________________________ in P.M. (day 4).
This results in ovulation approximately ______ hours after the prostaglandin administration. In superovulated animals, the ova are released over a __________ hour period.
Therefore, the cow can be inseminated _______ times, at _______hour intervals, 12 hours after the onset of standing heat.
Most cows will produce ___________ viable embryos, while others may produce very low numbers of embryos.
Heat Detection
Great attention should be placed on heat detection, semen selection, and proper semen handling. Proper heat detection involves three areas for consideration and attention:
List five signs which indicate the animal is approaching estrus:
1.
2.
3.
4.
5.
2. Donor animals should not be left alone (a group of approximately _______ other animals is sufficient).
3. Pens used should not be ____________________ or too _____________________.
Embryo Recovery:
The nonsurgical method for recovery of bovine embryos begins on _____________ after the onset of estrus.
Embryos produced before day 6 are usually found in the ____________________ and therefore would require surgical removal.
Benefits of this procedure when compared to surgical techniques include fewer adhesions, ability to perform the procedure under field conditions, less expensive, and presents fewer anesthetic risks.
The embryos collected can then either be __________________ or directly ___________________________________.
Transfer of Bovine Embryos
A common technique uses a _______________________ and either a 0.5 or 0.25 mL ______________________________.
With this procedure, each embryo is loaded into a straw, the cow is cleaned and the embryo is slowly deposited in the __________________________.
Costs
An average cost per pregnancy using ET can range anywhere from $_______________________.
The cost will vary greatly depending on the number of ________________________ per donor, the cost of the ________________________, and any collection, freezing and transfer ________________.
Increased ________________________________ (more heat detection, more insemination time, more times each animal must go through the chute, etc.) and costs for ____________________________________ programs should also be considered.
Do not forget that the most significant expense associated with ET will be the cost of owning and maintaining the necessary ____________________________________.
This can range anywhere from $_____________________ per year and would be in addition to the above costs for simply getting an ET pregnancy.