Efeito da progesterona exógena na produção de embriões em novilhas leiteiras
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Data
2010-08-27
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Universidade Federal de Goiás
Resumo
The reproductive and productive index of dairy cattle in Brazil are below the
desirable rates, and, in recent decades, the increase in milk production
occurred, partly, more because of the expansion of explored areas and the
increase of herds than due to an effective productive increment. The
development and application of reproductive biotechnologies are essential
conditions for improving reproductive efficiency, especially for domestic
ruminants, and techniques such as artificial insemination and embryo transfer
have been successfully used. Other biotechnologies such as in vitro embryo
production, cloning and genetic modification help to accelerate genetic
improvement, because they include animals with superior desirable traits,
although the results in terms of production are not so good. The main goal of an
embryo transfer program is to obtain a high number of viable embryos per
donor, after exogenous hormones administration, by increasing the number of
oocytes released, enabling the embryo transfer to recipient cows in order to
complete the gestation. Cows are born with more than 100,000 oocytes in
ovarian follicles, but by natural via, only 0.01% of viable products can be
generated, or a number close to 10 calves throughout their reproductive life.
One of the proposed solutions to this problem was the development of in vitro
production (IVP) of bovine embryos, a major biotech assisted reproduction,
which allows the interaction of sperm with oocyte outside the female
reproductive tract. Although these biotechnologies are used in many dairy and
beef herds, efficiency of an IVP program is limited, among other factors,
because of the oocyte recovery rates and the individual variation of ovarian
response to FSH treatment, requiring more studies to evaluate the association
between follicular waves and superstimulatory treatments, mainly in dairy
animals.
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SANTOS, Klayto José Gonçalves dos. Effect of exogenous progesterone on embryo production in dairy heifers. 2010. 124 f. Tese (Doutorado em Ciências Agrárias) - Universidade Federal de Goiás, Goiânia, 2010.