Abstract :
Llamas are monotocous and the length of their gestation period varies between 342 and
350 days. Thus the average number of offspring any female can produce throughout her
reproductive life is very limited to spread a desired genome. The multiple ovulation and
embryo transfer (MOET) technique allows an alternative to this limitation and reduces the
generation interval. The objective of this study was to evaluate embryo recovery in superstimulated
llamas which had previously been hormone-treated to inhibit follicular growth.
A total of 50 female llamas were monitored daily via rectal palpation and ultrasound and
divided according to their ovarian follicular growth into four phases. The females in each
phase were then randomly divided into two groups: A (n = 20) received a single dose of 1mg
of estradiol benzoate (EB) on the first day of the treatment + 100mgof progesterone (P4) i.m.
for 5 days with 5 animals per phase and B (n = 20) received 1mg EB at onset + 150mg P4 i.m.
for a period of 5 days with 5 animals per phase. Group C (n = 10) or control did not receive
any prior hormonal treatment and the females were in follicular phase I. All groups were
monitored daily and, in the presence of ovarian follicles smaller than the dominant size at
the end of treatment, all were superstimulated with 1000 IU eCG. For plasma progesterone
concentration recording, daily blood samples were collected from days−1 to 5 in the treated
females in Group A and B. No significant differences were observed regarding the inhibition
of follicle growth and in the plasma progesterone concentrations between Group A and
B. The ovarian response to superstimulation was 56.2%, 71.4% and 90%, with the average
number of dominant follicles produced per female being 4.4±0.9; 4.8±0.7 and 4.6±0.6 in
Groups A, B and C, respectively. The embryo recovery rate was 77.7%; 90% and 66.7% and the
average number of embryos recovered per female was 2.9±0.9; 2.6±0.9 and 2.4±0.8 for
Groups A, B and C, respectively. In Groups A and B, the static follicular phase (III) seemed to
be ideal for initiating the assisted reproductive technique of MOET. Although prior administration
of P4 + EB seems to have no effect on the number of females that responded to the
superstimulation treatments, the number of embryos recovered showed a tendency to be
higher when ovarian follicle growth inhibition was performed beforehand.
