RESUMO
We evaluated the relationship between plasma levels of anti-Müllerian hormone (AMH) and the number of antral follicles at the restart of the follicular wave in crossbred Holstein cows reared under extensive grazing systems over 2500 m above sea level. The study included 140 cows from 15 farms that were in average at the 75.3 ± 2.10 d post partum. Animals were synchronized according to the following regime: day 0 = intravaginal progesterone releasing device (IPD) + estradiol benzoate (EB); day 7: withdrawal of IPD + prostaglandin; and day 8: EB, for restart of the follicular wave on day 11. On this day 11, antral follicle counts (AFCs) were made by transrectal ultrasound, and a plasma sample was taken for the determination of AMH. The mean AMH plasma level was 0.06 ± 0.03 ng/ml and the mean AFC was 17.26 ± 0.38 follicles. A strong positive linear correlation was found between these two variables (r = 0.783, r = 0.613, P < 0.0001). Cows were categorized according to AMH concentration as high (>0.09 ng/ml), intermediate (0.09-0.05 ng/ml) or low (<0.05 ng/ml). Cows with high AMH presented a higher AFC (25.0 ± 2.21 follicles) than those with low AMH (14.08 ± 2.68 follicles; P < 0.001. Our results suggest that the cut-off value of AMH = 0.09 ng/ml may be useful for selecting donors in multiple ovulation embryo transfer programs involving cows with these characteristics. Our data further suggest that AMH plasma concentration correlates with AFC and can be used as an endocrine biomarker of the number of antral follicles present at a given moment of the estrous cycle in crossbred Holstein cows raised at altitudes above 2500 m.
RESUMO
Understanding the physiology of penile spicules in guinea pigs (Cavia porcellus) may improve their management in large-scale production guinea systems. Here we examined whether penis spicule development depends on testosterone and whether exogenous testosterone can reverse penile spicule atrophy in castrated guinea pigs. The relationship between total testosterone (TT) and the development of penile spicules (DPS) in guinea pigs was explored in two experiments. The first experiment described the TT and DPS curves in non-castrated guinea pigs (E1-G1) and guinea pigs castrated on day 35 (E1-G2). In the second experiment, the dose-dependent effect of the administration of exogenous testosterone (ET) was evaluated during DPS in Group 1 (E2-G1; castrated guinea pigs + 125 µg ET on days 65 and 80 of age), Group 2 (E2-G2; castrated guinea pigs + 250 µg ET on days 65 and 80 of age), Group 3 (E2-G3; non-castrated guinea pigs), and Group 4 (E2-G4; castrated guinea pigs without ET). Analysis of variance using a General Linear Model (GLM) was performed. TT increased from day 20 to day 35 in both groups in the first experiment (P > 0.05). This increase in TT was maintained in E1-G1 on days 50, 65, and 80; however, TT fell to basal values in E1-G2 after castration. DPS guinea was directly related to TT level. In Experiment 2, guinea E2-G1 and E2-G2 animals that received ET showed an increase in TT, significantly differing from E2-G4 (P < 0.05). Nevertheless, ET administration in E2-G1 and E2-G2 was not sufficient to reach the TT levels in E2-G3. DPS was closely related to TT levels, such that when testicles were removed, the spicules began to atrophy without disappearing. Our results suggest that TT in guinea pigs increases steadily until puberty completes, after which it decreases and stabilizes and shows an association with DPS. Furthermore, 12-35% of TT produced by guinea pigs is testicle-independent. Finally, ET administration can stop and reverse the spicule atrophy process in castrated males. These results will help to manage guinea pigs in a more sustainable way in countries where this species is of utmost relevance to provide the population with the meat of high quality.
