rate of early embryonic death is 25%. Average conception rate is 60
%. While 5-15 % is rate of failure of fertilization. EEM is a way to
get rid of undesirable genetic material at low biological cost
because animal is wasting 21 days of his life in EEM. On the other
hand if a cow born abnormal fetus, there will be a loss of 9 months.
Early embryonic mortality occurs between 8-19 days; mostly it occurs
at day 14, 15.
Causes of EEM
When the embryo is implanting, the first contact of fetus to uterus
sends signals to endometrium not to produce PGF2α so that
pregnancy may maintain. But if it is produced, the CL will regress
and embryo will die before the attachment. As a result animal will
come in heat at normal time in same cycle.
Nutrition deficiency is also the cause of EEM. Excess or deficiency
of β carotenes, phosphorus, copper, and selenium has been considered the cause of
Normal complement of chromosome is required for the proper
development of new born. Expression will not be normal if
chromosomes do not unite at proper site. First pair of chromosome
should unite with first pair of chromosome of opposite sex. If these
do not unite properly, it is cytogenic abnormality and embryo will
not be normal. If the pairs unite correctly but there may be
mutation, resulting embryo will be abnormal. Abnormal gametes can
fertilize but shortly after fertilization they will die. In cattle
10 % of embryos have abnormal karyotype.
Intrinsic factors include chromosomal abnormality, single gene
mutation, and mutagen induced irreversible changes in DNA.
Chromosomal abnormalities either inherited or arise during
gametogenesis. Some abnormalities may be acquired e.g. handling of
embryos during transfer, permanent alterations in DNA induced by
substances like superovulatory hormones, culture media and serum,
UV, DNA binding dyes, radio activity, ethylene oxide and viral
When foreign body enters in body there is reaction. When fetus comes
in uterus then there is no immune response because uterus has its
own immunosuppressive mechanism. If any defect in this system, it
will result in early embryonic mortality.
Cows which are older have higher incidence of early embryonic
Breed does not affect rate of embryonic mortality. Those herds which
have higher incidence of inbreeding have more chances of EEM.
If environment of uterus is not proper, animal will not survive.
There are two things for development of embryo.: