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Pregnancy diagnosis by transrectal ultrasonography (using a 5 MHZ linear
probe ) presented the maximum sensitivity and negative predictive values at day 26 and
day 29 after estrus in heifers and cows , respectively .
Palpation per rectum using the fetal membrane slip for pregnancy diagnosis did
not increase embryo /fetus mortality when compared with a positive control group of
non -palpated females . The use of a controlled randomized block design was a useful
approach to study this problem . Blocking for category and number of embryos allowed
us to remove these confounding factors .
Factors that affected pregnancy loss during the first four months of pregnancy
were : period of pregnancy , age of the animal , number of previous lactations and number
of embryos . Pregnancy loss was higher during the embryonic than fetal periods .
Spontaneous embryo /fetal mortality increased with the age of the animal and lactation
number . The risk of spontaneous embryo /fetus mortality was higher in twin than in
single pregnancies .
Two types of embryo /fetus mortality were noted : Type I and Type II . Type I was
characterized by presence of positive fetal membrane slip by palpation per rectum , signs
of degeneration by transrectal ultrasonography and persistence of a functional corpus
luteum . The uterus took approximately 3 weeks to be noted clean by transrectal
ultrasonography and the animals showed estrus one month after the conceptus was
diagnosed dead . Type II was characterized by absence of positive signs of pregnancy by
palpation per rectum , absence of signs of degeneration by transrectal ultrasonography
and absence of a functional corpus luteum .
Pregnancy loss in nuclear transfer derived embryos was higher compared to in
vivo derived embryos produced by artificial insemination . Pregnancy loss occurred
mainly during the transition from the embryonic to the fetal period . Embryo /fetus
mortality detected was Type I . Progesterone produced by the corpus luteum was noted at
pregnancy levels for approximately two weeks after embryo /fetus death . Protein B , a
hormonal placental marker , was maintained at pregnancy levels for approximately 3
weeks after embryo /fetus death . No differences in the levels of the two hormones were
noted when comparing females with dead or live conceptuses . |
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