Effect of estradiol cypionate and GnRH treatment on plasma estradiol‐17β concentrations,synchronization of ovulation and on pregnancy rates in suckled beef cows treated with FTAI‐based protocols |
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| Authors: | G Uslenghi A Vater S Rodríguez Aguilar J Cabodevila S Callejas |
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| Institution: | 1. CONICET fellowship (CIVETAN), Campus Universitario, Tandil, Buenos Aires, Argentina;2. área de Reproducción, Centro de Investigación Veterinaria de Tandil, (CIVETAN, CONICET‐CICPBA), FISFARVET, Fac. de Cs. Veterinarias, U.N.C.P.B.A, Tandil, Buenos Aires, Argentina;3. Private practice, Buenos Aires, Argentina |
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| Abstract: | Two experiments were conducted to evaluate the effect of different ovulation inducers on E‐17β plasma concentrations, synchronized ovulations and pregnancy rates. In Experiment 1, cows received a progesterone intravaginal device (PID) with 1 g of progesterone (P4) plus 2 mg of estradiol benzoate (EB) (day 0). At PID removal (day 8), cows received 0.150 mg of D‐cloprostenol and were randomly assigned to four treatment groups (n = 10/treatment): Group ECP: 1 mg of estradiol cypionate at PID removal, Group EB: 1 mg of EB 24 hr after PID removal, Group GnRH: 10 μg of GnRH 48 hr after PID removal, Group ECP‐GnRH: 1 mg of ECP at PID removal plus 10 μg of GnRH 48 hr later. Ultrasonographic examinations were performed to detect the dominant follicle and ovulation. GnRH‐treated cows ovulated later (p < .05) compared to ECP‐ and ECP+GnRH‐treated cows. There were effects of treatment, time and their interaction on E‐17β concentrations (p < .05). ECP treatment affected plasma E‐17β concentration, which increased earlier and decreased later compared to treatments without ECP. In Experiment 2, cows received (i) ECP: n = 126; (ii) EB: n = 126; (iii) GnRH: n = 136; (iv) ECP+GnRH: n = 139; FTAI was performed 48–50 hr after PID removal. Pregnancy rates did not differ among ovulation inducers (p > .05; ECP: 54.0%, 68/126; EB: 49.2%, 62/126; GnRH: 40.4%, 55/136; ECP+GnRH: 43.9%, 61/139). In conclusion, ECP administration (ECP and ECP+GnRH treatments) affected E‐17β concentrations, determining its earlier increase and later decrease compared to treatments without ECP (EB and GnRH treatments). ECP+GnRH‐treated cows achieved the best distribution of ovulations without affecting pregnancy rates. |
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