- -  AGRICULTURE CORE CURRICULUM  - -

(CLF3000)  Advanced Core Cluster:  ANIMAL SCIENCE

  (CLF3250)  Unit Title:  LIVESTOCK BREEDING AND GENETICS

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  (CLF3256)  Topic:  EMBRYO TRANSFER             Time          Year(s) 
                                                1 hour          3 / 4        
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          Topic Objectives:  Upon completion of this lesson, the student
                             will be able to:

          Learning Outcome #:

            (D-11)  -  Describe a surgical and a nonsurgical method of 
                       embryo transfer and explain the impact that embryo
                       transfer has made on the animal genetics industry.

          Special Materials and Equipment:  VEP Filmstrip, "Embryo Transfer
                       of Beef and Dairy Cattle".

          References:  Ensminger, M.E. (1983). THE STOCKMAN'S HANDBOOK (6th 
                         ed.).

          Evaluation:  Quiz by instructor.


TOPIC PRESENTATION:  EMBRYO TRANSFER

A.  Introduction

    1.  Embryo transfer can also be called "ova" transplantation.        

        a.  It involves removing fertilized eggs from a female (donor) and
            placing them in recipient females.

        b.  It is most widely practiced in beef and dairy cattle currently,
            but procedures are now available commercially for all livestock
            species and several laboratory animal species (used mainly for 
            research purposes).

B.  The Process of Embryo Transfer

    1.  Superovulation:

        a.  The donor is stimulated to cow ovulate more than the normal 
            number of just one egg per cycle.

        b.  Hormone preparations are injected intramuscularly to
            cause superovulation.  The most common sources of such hormones 
            are PMSG (pregnant mare's serum gonadotropin) or FSH (follicle
            stimulating hormone).

    2.  Insemination:

        a.  The donor cow (which was superovulated) is either bred by the
            bull, or 

        b.  inseminated artificially.

    3.  Ova collection:

        a.  There are 2 methods -

            1)  Surgical, the ova are collected from the donor cow's 
                reproductive tract surgically (a very expensive method). 

            2)  Nonsurgical, the ova are flushed from the reproductive tract 
                using a saline solution (currently the standard method).

    4.  Implantation:

        a.  Each of the recipient cows must be at the proper stage in her
            estrous cycle to receive an embryo.  Recipients are synchronized  
            with the donor cows using hormone treatment.

        b.  The eggs are transferred to the recipient cows using a 
            non-surgical technique.

C.  The Impact of Embryo Transfer

    1.  Benefits:

        a.  A dozen calves might be obtained from a valuable cow in one 
            year.

        b.  The rate of progress of genetic improvement would quicken
            because of increased progeny from valuable animals.

        c.  Valuable cows that produce normal ova but fail to conceive due
            to some hormonal or anatomical defects would not need to be
            culled because of sterility.  Such animals could be used as
            donors for supplying ova for transfer.  (Before this is done,
            however, it should be determined whether or not the reproductive 
            problem is genetically-related.  If it is, the animal is 
            probably not a desirable candidate.)

        d.  Progeny testing of heifers could be done much more quickly if
            large numbers of fertilized eggs could be procured from young 
            heifers and transferred into mature recipients.

        e.  Genetically inferior animals could be made more productive by
            using them as recipient animals, as long as there is a 
            sufficient supply of fertilized ova for the transfer process.

    2.  Limitations:

        a.  The current process is expensive.


        b.  The technique for harvesting the ova is quite complicated and 
            technical in nature.

        c.  There is a possibility that donor cows used repeatedly may 
            become incapable of carrying young to full term in their own 
            uterus.

          __________________________________________________________
          ACTIVITY: 
 
          1.  Show the VEP filmstrip, "Embryo Transfer of Beef and
              Dairy Cattle."           
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5/2/90sg


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