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COLLECTION: GOAT HANDBOOK
ORIGIN: United States
DATE INCLUDED: June 1992
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.
DOCN 000000033
NO D-7
ESTRUS SYNCHRONIZATION AND EMBRYO TRANSFER
M. C. Smith; Cornell U., Ithaca, NY
R.E. McDowell; Cornell U., Ithaca, NY
Genetics and Reproduction
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++++
ESTRUS SYNCHRONIZATION AND EMBRYO TRANSFER
COLLECTION;GOAT HANDBOOK
ORIGIN;United States
DATE_INCLUDED;June 1992
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