Abstract
We determined if laterality of ovulation and intrauterine embryo location differentially induces changes in the mesometrial/endometrial vascularization area (MEVA) between uterine horns, during and after embryo migration, elongation and implantation in llamas. Adult, non-pregnant and non-lactating llamas (n = 30) were subjected to daily B-mode ultrasound scanning of their ovaries. Llamas with a growing follicle ≥8 mm in diameter in the left (n = 15) or right (n = 15) ovary were assigned to a single mating with an adult fertile or vasectomized male. Power-doppler ultrasonography was used to determine the MEVA in a cross section of the middle segment of both uterine horns. MEVA was determined by off-line measurements using the ImageJ software. MEVA measurements were performed before mating (day 0) and on days 5, 10, 15, 20, 25, and 30 after mating in pregnant [llamas with left- (n = 6) or right-sided (n = 6) ovulations] and non-pregnant [llamas with left- (n = 6) or right-sided (n = 6) ovulations] females. Ovulation was confirmed by the disappearance of a follicle (≥8 mm) detected previously. Pregnancy was confirmed by the presence of the embryo proper. MEVA was analyzed by one-way ANOVA for repeated measures using the MIXED Procedure in SAS. If significant (P ≤ 0.05) main effects or interactions were detected, Tukey's post-hoc test for multiple comparisons was used. Ovulation rate did not differ (P = 0.4) between females mated to an intact or vasectomized male and between right- or left-sided ovulations. Three females mated to the intact and 3 to the vasectomized male did not ovulate and were excluded of the study. First observation of fluid inside the gestational sac and of embryo proper, were made exclusively in the left uterine horn, on day 15.8 ± 3.8 and 22 ± 2.7, and 16.7± 2.6 and 27.5 ± 2.8 for pregnant llamas ovulating in the right and left ovary, respectively. Although the MEVA of both uterine horns was affected by time (P < 0.05), it was not affected by physiological status (pregnant vs. non-pregnant; P = 0.9) or laterality of ovulation (P = 0.4). Contrary to expectations, regardless of the laterality of ovulation, in pregnant llamas the left horn did not display a greater MEVA before or after embryo arrival, a trend that was observed during the first 30 days of gestation.
Highlights
Llamas and alpacas have several unique reproductive characteristics, one of which is the establishment of embryo implantation and gestation exclusively in the left uterine horn, regardless of laterality of ovulation [1,2,3]
6/8 and 6/7 llamas with a preovulatory follicle ≥8 mm diameter located either in the right or left ovary ovulated after mating with the vasectomized male
First observations of fluid inside the gestational sac and the embryo proper were recorded on day 15.8 ± 3.8 and 22 ± 2.7, and 16.7± 2.6 and 27.5 ± 2.8, for pregnant llamas ovulating in the right and left ovary, respectively
Summary
Llamas and alpacas have several unique reproductive characteristics, one of which is the establishment of embryo implantation and gestation exclusively in the left uterine horn, regardless of laterality of ovulation [1,2,3]. Females from both species have a bicornate uterus that presents a clear asymmetry between uterine horns, with the left horn being larger than its right counterpart [4, 5]. Ovulation occurs with the same frequency in the left and right ovary [2, 6], embryos originated from right-ovary ovulations must migrate into the left uterine horn before the day of the beginning of luteolysis (Day 9 after ovulation) for the pregnancy to be successfully established [3, 7]
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