RESUMO
This study was performed to evaluate plasma concentrations of anti-Mullerian hormone (AMH) and the ovarian antral follicle population (AFP) in different genetic groups. Cyclic heifers (13 Bubalus bubalis [Murrah]; 15 Bos taurus [Holstein] and 10 Bos indicus [Gyr]) were maintained under the same management and were synchronized with two doses of 150 µg IM d-cloprostenol administered 14 days apart. After the second d-cloprostenol treatment, heifers had their ovaries scanned daily by ultrasound to define the day of ovulation. On the same day, the AFP was determined and a plasma sample was collected to measure AMH. Murrah heifers had less AFP (25.6 ± 2.1 follicles; p = 0.01) and plasma AMH concentration (0.18 ± 0.03 ng/ml; p < 0.001) than Gyr (60.0 ± 12.2 follicles and 0.60 ± 0.12 ng/ml of AMH); however, data were similar when compared to Holstein (35.9 ± 6.8 follicles and 0.24 ± 0.06 ng/ml of AMH) heifers. Regardless of genetic background, there was a positive relationship between the AFP and plasmatic AMH concentration (Murrah [r = 0.62; p < 0.01], Holstein [r = 0.66; p < 0.001] and Gyr [r = 0.88; p < 0.001]). Also, when heifers were classified according to high- or low-AMH concentration based on the average within each genetic group, high-AMH heifers had greater (p < 0.0001) AFP than low-AMH heifers. In conclusion, both Murrah and Holstein heifers presented lower plasma AMH concentration and AFP when compared to Gyr.
Assuntos
Hormônio Antimülleriano/metabolismo , Búfalos/metabolismo , Bovinos/metabolismo , Cloprostenol/farmacologia , Folículo Ovariano/efeitos dos fármacos , Criação de Animais Domésticos , Animais , Búfalos/sangue , Bovinos/sangue , Sincronização do Estro/métodos , Feminino , Folículo Ovariano/fisiologia , Especificidade da EspécieRESUMO
The present study aimed to evaluate the efficacy of different inducers of new follicular wave emergence (FWE) and ovulation in fixed-time artificial insemination (FTAI) synchronization protocols using norgestomet ear implants (NORG) in Bos indicus cattle. In Experiment 1, the synchronization of FWE was evaluated when two different estradiol esters in different doses [2mg estradiol benzoate (EB), 2.5mg EV or 5mg estradiol valerate (EV)] were administered with NORG implant insertion in B. indicus cattle (estrous cyclic heifers and cows with suckling calves; n=10 per treatment). After estradiol treatment, ovarian ultrasonic exams were performed once daily to detect the interval between treatment and FWE. There were significant treatment-by-animal category interaction (P=0.05) on the interval from the estradiol treatment to FWE. An earlier (P<0.0001) and less variable (P=0.02) interval from estradiol treatment to FWE was observed in heifers treated with EB (2.5±0.2; mean±SE) than in those treated with 2.5mg EV (4.2±0.3) or 5mg EV (6.1±0.6). Cows treated with 5mg EV (4.0±0.5) had longer (P=0.05) interval than cows receiving EB (2.5±0.2), however, there was an intermediate interval in those cows treated with 2.5mg EV (3.1±0.4). In Experiment 2, the number of uses of the NORG implant (new; n=305 or previously used once; n=314) and three different ovulation induction hormones [0.5mg estradiol cypionate (EC) at implant removal (n=205), 1mg EB given 24h after implant removal (n=219), or 100µg gonadorelin (GnRH) given at FTAI (n=195)] were evaluated in Nelore heifers (2×3 factorial design). Similar pregnancy per AI (P/AI; 30 days after FTAI; P>0.05) were achieved using each of the three ovulation induction hormones (EB=40.6%; EC=48.3%, or GnRH=48.7%) and with a new (47.2%) or once-used NORG implant (44.3%). In Experiment 3, the effect of different ovulation induction hormones for FTAI [1mg EC at NORG implant removal (n=228), 10µg buserelin acetate at FTAI (GnRH; n=212) or both treatments (EC+GnRH; n=215)] on P/AI was evaluated in suckled beef cows treated with a once-used NORG implant and EB to synchronize the FWE. Similar P/AI (P=0.71) were obtained using GnRH (50.9%), EC (51.8%) or both treatments (54.9%) as ovulation induction hormones. Therefore, both doses of EV (2.5 or 5.0mg) with NORG implant delayed and increased the variation of the day of new FWE compared with EB in B. indicus cattle. These effects were more pronounced in B. indicus heifers than cows. Synchronization protocols for FTAI with either a new or once-used NORG implant with EB at insertion to induce a new FWE and either the use of EB, EC or GnRH as ovulation induction hormones may be successful in B. indicus heifers. Also, when a once-used NORG implant was used, either the administration of EC, GnRH or both as ovulation inducers resulted in similar P/AI in suckled B. indicus cows, showing no additive effect of the combination of both ovulation induction hormones.