Agriculture Reference
In-Depth Information
following sponge withdrawal or a single insemination 54
hours following sponge withdrawal. Only semen with a
motility score of 3 (out of a scale of 5) and above is suit-
able for use in an AI program.
In conclusion, it can thus be said that the success of an
AI program depends exclusively on the care and accuracy
with which it is applied. Moreover, fertility results that
vary between 60 and 90% are common when fresh semen
is used. Correctly applied, AI can only be benefi cial to the
goat industry worldwide (Evans and Maxwell, 1987;
Greyling and Grobbelaar, 1988; Wildeus, 1999; Hafez and
Hafez, 2000 ).
resulted in low ovulation rates and were accompanied by
the occurrence of a high number of large unovulated fol-
licles. Later studies revealed an increased ovulation rate,
ova recovery rate, and number of transferable embryos that
could be obtained using pure FSH. Trials on the superovu-
latory response in goats to these exogenous gonadotro-
phins revealed an ovulatory response per doe of 16.6 for
pFSH and 11.7 for PMSG or eCG. Factors affecting the
superovulatory response also include individual variation
in terms of response within a specie and seasonality (Table
7.9 and Table 7.10) (Van der Nest, 1997; Hafez and Hafez,
2000 ).
Fertilization in superovulated does (donors) can be
achieved by using three methods, namely natural mating,
cervical insemination, or intrauterine (laparoscopic)
insemination. In goats, the technique of laparoscopy is
usually implemented for intrauterine insemination because
it yields a very high fertilization rate with lower insemina-
tion doses (36 to 48 hours following intravaginal proges-
tagen removal) being required.
Generally surgical fl ushing of embryos in goats is per-
formed 6-7 days following AI. The fl ushings are collected,
the embryos recovered and examined, and then evaluated.
Prior to fl ushing, the number of CL on each ovary serves
as an indication of the ovulation rate and the possible
number of embryos that could possibly be recovered. A
recovery rate of 80% and more is acceptable in the retrieval
of embryos (Warnes et al., 1982; Greyling et al., 2002).
Only high quality embryos (Grades or Classes I and II) are
generally used for fresh embryo transfer to synchronized
recipients within 5 hours of fl ushing (Table 7.11). Embryos
at this stage of development postestrus include the follow-
ing developmental stages: (1) compact morula, (2) early
blastocyst, or (3) expanded blastocyst with no signs of
degeneration, protruding cells, or vacuolization of the
blastomeres. Recipients responding to synchronization
(showing estrus) receive two embryos by laparoscopy (one
per uterine horn). The kidding performance of recipients
and the survival of embryos has a major effect on the
profi tability and success of any embryo transfer program.
A pregnancy rate of 60% and higher is acceptable in a
MOET program with goats. The overall ovulation rate,
embryo recovery rate, and pregnancy rates obtained in
goats demonstrates MOET as an effective and acceptable
accelerated breeding technique (Table 7.12 ) (Holtz, 2005 ;
Melican and Gavin, 2008 ).
Multiple Ovulation and Embryo Transfer (MOET)
in Goats
One of the most exciting developments in the reproduction
of farm animals is embryo transfer, the so-called second
generation reproductive biotechnology, after artifi cial
insemination (AI). The successful transfer of embryos is
largely dependent on the selection of acceptable donor and
recipient does. Generally more inferior does in terms of
genetic traits are used as surrogate females. However,
these recipient animals should still be fertile, show good
mothering ability, and produce adequate milk for sustain-
ing their young. Survival of the transferred embryos is
maximized if the recipients are synchronized to show
estrus on the same day or one day after the donor.
The major problem in the use of MOET is the variable
ovulatory response to superovulation in the donor animals.
The superovulation rates in goats can vary from 1-18
ovulations, depending on the dosage and type of exoge-
nous hormones used. These ranges may, however, also be
infl uenced by several factors, including season of treat-
ment, body condition of the doe or plane of nutrition, and
method of breeding. Genetic effects, age, and type of
gonadotrophin agents used may also contribute to this
variation in ovarian response (Warnes et al., 1982). Embryo
recovery rates have improved over the years, and with the
development of laparoscopy, it has now become possible
to collect embryos from the same female donor repeatedly,
with the minimum complication of adhesions. Repeated
hormonal superstimulation on the same individual has,
however, been reported to lead to a decreased ovarian
response due to an immune response by the donor
(Lehloenya, 2008 ).
The superovulatory treatment of does aims at producing
the maximum number of viable oocytes within one estrous
period. The most commonly used gonadotrophins in
embryo transfer programs are eCG (PMSG) or FSH.
Experiments using eCG (long half-life) have generally
Accelerated Kidding
With most goats (with maybe the exception of the Angora
doe), being polyestrous and having an extended breeding
