Abordagens para reverter casos de infertilidade em vacas leiterias: Inseminação artificial intrafolicular e exposição prolongada a estrógenos

Abstract

Infertility problems are common in dairy cows, especially on high-yielding cows, who have accelerated metabolism of steroid hormones, such as estradiol (E2) and progesterone (P4). Techniques such as intrafollicular artificial insemination (IFAI) and prolonged exposure to estrogens in artificial lactation induction (ALI) protocols have shown promising results as alternatives to reverse previous infertility. In a first study, the objective was to evaluate sperm motility in vivo after IFAI or after incubation in follicular fluid in vitro. Aspiration to recover follicular content was conducted 1 to 4 h after IFAI to evaluate sperm motility. Thereafter, kinetics of pooled spermatozoa from commercial frozen-thawed semen doses were evaluated after incubation in follicular fluid (FF) or pure (control) for 1 to 3 h. Reduced sperm motility was observed both in vitro and in vivo, leading to the conclusion that both ovarian follicles and FF do not provide an adequate environment to maintain bull sperm motility. The second study had the objective to determine the serum levels of E2 and P4 in cows submitted to long periods of estrogen exposure and to identify changes in the gene and cell profile of the endometrium of cows exposed to ALI. Cows presented 51.4 ± 11,0 pg/ml of E2 at the D0, but achieved greater levels at days 2, 4, 8, 10 and 13 (P <0.05), reaching up to 4,000 pg/ml at D4. Levels of P4 were greater than 6 ng/ml at D0 and during the entire treatment period, returning to basal levels at D8. After treatment, the OXTR receptor (oxytocin) presented lower expression (P <0.05), whereas the PGR (progesterone) receptor and the SERPINA14 gene presented a slightly increased expression (P <0.07). The gene modulation of the OXTR, PRG and SERPINA14 receptors suggests that prolonged estrogen exposure influences the uterine environment of cows submitted to ALI, with positive effects on their subsequent fertility. Prolonged estrogen exposure was not able to induce modifications in the cell pattern and immune response in the endometrium of cows in proestrus after treatment. The present study provides information on the use of IFAI in cattle for future studies. Furthermore, it provides data regarding the endocrine profile of cows exposed to prolonged exposure to estrogens, as well as the changes promoted by this exposure in the gene expression of the endometrium and its cellular profile.