Embryo production in superstimulated llamas pre-treated to inhibit follicular growth

CARRETERO MI; MIRAGAYA MH; CHAVES MG; GAMBAROTTA MC; AGÜERO A

JOURNAL OF SMALL RUMINANT RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2010 vol. 88 p. 32 - 37

0921-4488

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.