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"Estrus Synchronization and Embryo Transfer"

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Estrus Synchronization and Embryo Transfer

By: "Goat Handbook, United States, 1992"

  • About the Author
  • 1) In temperate climates, most goats are seasonally polyestrous. They exhibit cyclic heats during the fall months, under the influence of decreasing day length. Sometime between January and March, as days lengthen, the typical goat enters into a period of anestrus. The physiological differences between the breeding and the anestrus seasons necessitate the use of different techniques for the control of estrus during each time period.

    2) Reasons for Synchronizing Estrus During the breeding season, estrus synchronization permits the efficient use of artificial insemination and of a trained technician. Owners with full time jobs can schedule breedings, artificial or natural, for weekends or vacation periods. In herds or animals where heat detection is difficult, goats may be successfully bred even though they cannot be found in heat. Does may be bred to kid at a certain time, for instance to take advantage of the Easter market for sale of buck kids. Five months after synchronized breeding, parturitions will be closely grouped or can be further synchronized by the use of hormone injections. Additional advantages are the simplification of kid rearing and the control of diseases such as bacterial scours and coccidiosis afforded by an all in, all out, kid raising program. Finally, estrus synchronization is an important tool for embryo transfer procedures.

    3) Outside the normal breeding season, synchronization has additional advantages. It permits the breeding of does to freshen in the fall, thereby assuring a supply of milk when most of the herd is dry. In areas with a demand for goat milk, there may be an economic incentive in the form of higher prices paid for winter milk.

    4) An alternative to synchronization that permits breeding during the spring months is the use of lights. If goats are kept under long days (16-20 hours) for several months (for instance, January and February) and then returned to ambient day length, many will exhibit fertile cycles during the next few months. If natural breeding is to be used, it is imperative that the buck also be subjected to the controlled lighting. This is not a synchronization technique, as the induced estrus periods will be somewhat randomly spaced.

    5) Methods of Synchronization Does to be synchronized should be placed on a high energy diet 2 to 4 weeks before breeding is desired. Anthelmintics, if needed, also should be administered in advance. In general, best results will be obtained with normally fertile does for which the most recent parturition was without complications. Polled animals with both parents polled should be examined first before commencing with synchronization to eliminate intersexes and sterile animals. Polled animals with masculinized anatomy, masculine behavior, or a total absence of estrus periods prior to synchronization are poor candidates for synchronization and the probability of successful breeding is greatly reduced.

    6) The Buck One of the simplest means of synchronization is the sudden introduction of a buck or his odor early in the fall. It has been shown that many does will come into estrus approximately 8 to 10 days later. If a teaser buck is first introduced and then replaced after 3 weeks by a fertile male, reasonably good synchronization and an increased ovulation rate will be achieved on the second cycle. If does are already cycling, the synchronization effect will be largely lost.

    7) Vaginal Sponges In France, synchronization of goats is commonly obtained by the use of intravaginal sponges. They are available commercially abroad and are impregnated with 45 mg of fluorogestone acetate. Sponges with less hormone (marketed for sheep) give lower conception rates. The sponge is coated with an antibiotic powder or ointment and is placed deep in the vagina for 17 to 21 days. The string designed for removal of the sponge should be cut short unless each goat is housed separately. When the sponge is removed, it will be covered with a purulent exudate, but this exudate does not interfere with conception and no further treatment is necessary.

    8) Hormone injections are used to stimulate follicular development when the sponge is removed. Pregnant mare serum gonadotrophin (PMSG) is preferred but is often hard to obtain in the United States. It is available from Francea (as are the sponges), but a permit from the USDAb is required for importation of the hormone and may be impossible to obtain. The dose of PMSG used depends on the age of the goat, the current milk production, and the season of the year. In dairy breeds, fertility is poor during the first 4 months after parturition. Adults for AI giving more than 8 pounds of milk a day receive 700 IU of PMSG during the period from March 15 to June 14, 600 IU from June 15 to September 14, and 500 IU during the fall breeding season. Does milking less heavily receive 100 IU less during each time period, as do adults that are to be serviced naturally. Overdosing results in superovulation and potential abortion due to uterine crowding. Doelings receive 400 IU of PMSG during all seasons, but it is important that these animals weigh at least 77 lbs (European breeds) before hormonal treatment is attempted.

    9) During the anestrous season, the PMSG is administered 48 hours before sponge removal. During the breeding season, this treatment is given simultaneously with sponge removal. The goats are generally in heat 12 to 36 hours after sponge removal, and are bred within 48 hours. If fixed time insemination is to be used, 2 breedings at 31 and 55 hours or 36 and 60 hours have been recommended.

    10) Limited trials have been performed substituting follicle stimulating hormone (FSH) for the PMSG, using 2 doses of 2 mg each at 12 hour intervals. The FSH appears to be less effective than PMSG.

    11) Progesterone Treatments A removable subcutaneous implant containing progesterone or other progestogen in silastic tubing can be substituted for the vaginal sponge. This technique avoids vaginal infections as well as the rare occurrence of adhesions preventing sponge removal, particularly in doelings. Another technique involves the subcutaneous or intramuscular administration of progesterone in oil, 20 mg every other day for 18 days. Where it is available, the oral use of 6-methyl-17-acetoxy-progesterone (MAP) at 50 mg/day for 15 to 20 days is yet another option. With all these products, PMSG will improve fertility.

    aDr. D. Aguer Intervet - SA 43, Avenue Joxe B.P.
    235 49002 Angers, France.

    bHarvey A. Kryder, Jr. Chief Staff Vet. Organisms & Vectors.
    U.S. Dept. Agriculture. Animal & Plant Health
    Inspection Service, Federal Center Building.
    Hyattsville, Maryland 20782.

    12) ++++MISSING DATA++++

    13) The donor doe is anesthetized 3 to 5 days after mating, using halothane or barbiturates. A midventral or flank laparotomy incision permits flushing of the oviducts and uterine horns for the recovery of fertilized eggs. Approximately 10 ml of tissue culture medium 199 with sodium bicarbonate (and, in some studies, 10 2.256835e+199oat serum) at 37 used to flush each oviduct. The fluid is collected in a petri dish and examined under a binocular dissecting microscope to identify ova that have undergone cleavage. These fertilized eggs are picked up in a 20 gauge needle or special pipette in preparation for transfer. Recovery rates of 60 to 80(based on number of corpora lutea) and 80 of recovered eggs have been reported.

    14) Meanwhile, recipient does must be prepared. If a large herd of normal, cycling does is available, animals with natural heats 24 hours before to 36 hours after the estrus of the donor doe are selected. Otherwise, recipients are synchronized using any of the techniques described previously. Both progesterone and prostaglandin treatments have been ++++MISSING DATA++++

    Rated 4.9 by 131 responses.

    About the Authors: Extension Goat Handbook - This material was contributed from collections at the National Agricultural Library. However, users should direct all inquires about the contents to authors or originating agencies.
    M. C. Smith; Cornell U., Ithaca, NY
    R.E. McDowell; Cornell U., Ithaca, NY.

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