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This study aimed to investigate the effect of three different doses of estradiol-17ß on ovulation and subsequent luteal development and function in llamas. Twenty-three llamas were examined daily by transrectal ultrasonography until the detection of an ovulatory follicle (≥8 mm). Thereafter, animals were divided into five groups: Control (n = 3; treated with 1.6 ml of saline solution), GnRH group (n = 6, treated with an intravenous injection of 8.4 µg Buserelin), and estradiol groups that received 0.6 mg (E1, n = 4), 1 mg (E2, n = 4), or 1.6 mg (E3, n = 6) of estradiol-17ß intravenously. Detection of ovulation was based on ultrasonographic visualization of disappearance of the largest follicle and subsequent presence of a newly formed corpus luteum (CL) and progesterone concentration exceeding 1 ng ml-1. Daily blood samples were collected to determine plasma progesterone concentration. Ovulation rate was 0% for control and E1 groups, 25% for E2 group, and 100% for GnRH and E3 groups. Differences in the mean CL diameter between GnRH and E3 groups were not statistically significant. Plasma progesterone concentration was similar between groups during the different days in ovulated animals. However, the day that the plasma progesterone concentration was above 1 ng ml-1 and the day that the highest plasma progesterone concentration was achieved differed among E3 and GnRH groups, occurring later in females treated with estradiol. In conclusion, an injection of estradiol-17ß is capable of inducing ovulation in llamas and the response depends on the dose used. Most of the animals required the highest tested dose (1.6 mg) to induce the ovulatory process. Although the CL diameter in females induced to ovulate with estradiol was similar to that in llamas induced to ovulate with a GnRH analog, the rise in plasma progesterone concentration above 1 ng ml-1 and the peak progesterone concentration were attained 1 day later in the estradiol treated females.

RESUMEN

Mycobacterium cell wall fraction (MCWF) is a biological component made up of molecules with immunostimulant properties, which is therapeutically used to modulate persistent breeding-induced endometritis (PBIE). The aim of this study was to analyze the effect of this immunomodulator on the endometrial histological structure during the diestrus of PBIE-resistant and -susceptible mares that either received treatment with MCWF or not. The experiment was conducted with 10 resistant mares (RM) and 9 susceptible mares (SM). In the first estrous cycle of the trial, all mares were inseminated with dead semen as an inflammatory stimulus (Group A); at the next cycle, all mares were inseminated with dead semen and treated with a MCWF commercial immunomodulator (Group B). In both groups, endometrial biopsies were taken on day 7 post-ovulation (diestrus). Endometrial biopsies of untreated-RM (UTRM, n = 6), untreated-SM (UTSM, n = 7) MCWF-treated-RM (TRM, n = 6) and MCWF-treated-SM (TSM, n = 6) were evaluated. They were randomly chosen as representative mares of Group A and B, respectively. The height of lining and glandular epithelia, glandular diameter, glandular density and glandular area were evaluated. The histological structure revealed lymphocytic infiltration and dilated, tortuous glands with some glandular nests, particularly in UTSM. The histomorphometrical results showed no differences (ρ > 0.05) between the analyzed groups. This would indicate that post-service treatment with the MCWF immunomodulator does not modify the endometrial histoarchitecture but, apparently, its action would be mainly based on the stimulation of the cellular and humoral immune responses.

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RESUMEN

BACKGROUND: Llamas (Lama glama) are induced ovulators and the process of ovulation depends on dominant follicular size. In addition, a close relationship between behavioural estrus and ovulation is not registered in llamas. Therefore, the exogenous control of follicular development with hormones aims to predict the optimal time to mate. Oestradiol-17beta (E2) and its esters are currently used in domestic species, including camelids, in synchronization treatments. But, in llamas, there is no reports regarding the appropriate dosages to be used and most protocols have been designed by extrapolation from those recommended for other ruminants. The aim of the present study was to characterize plasma E2 concentrations in intact female llamas following a single intramuscular (i.m.) injection of two oestradiol esters: oestradiol benzoate (EB) and oestradiol cypionate (ECP). METHODS: Twelve non pregnant and non lactating sexually mature llamas were i.m. injected on day 0 with 2.5 mg of EB (EB group, n = 6) or ECP (ECP group, n = 6). Blood samples were collected immediately before injection, at 1, 6, 12, 24 h after treatment and then daily until day 14 post injection. Changes in hormone concentrations with time were analyzed in each group by analysis of variance (ANOVA) using a repeated measures (within-SS) design. Plasma E2 concentrations and area under the concentration-time curve (AUC) values were compared between groups by ANOVA. In all cases a Least-Significant Difference test (LSD) was used to determine differences between means. Hormonal and AUC data are expressed as mean +/- S.E.M. RESULTS: Peak plasma E2 concentrations were achieved earlier and were higher in EB group than in ECP group. Thereafter, E2 returned to physiological concentrations earlier in EB group (day 5) than in ECP group (day 9). Although plasma E2 profiles differed over time among groups there were no differences between them on AUC values. CONCLUSIONS: The i.m. injection of a single dose of both oestradiol esters resulted in plasma E2 concentrations exceeding physiological values for a variable period. Moreover, the plasma E2 profiles observed depended on the derivative of oestradiol administered. This basic information becomes relevant at defining treatment protocols including oestrogens in llamas.

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