RESUMO
Although combining of eCG and hCG administrations is known to enhance LH-like actions, there have been few studies where there was comparison of the effects of treatment of anestrous ewes with eCG and hCG and eCG alone. In Experiment 1, 18 ewes in seasonal anestrus were administered an intravaginal device (IVD) containing medroxyprogesterone acetate for 12 days, and at the time of IVD removal (D0), were allocated into the following groups (n = 6/group): no further treatment (control); 400 IU eCG (eCG); or 400 IU eCG and 200 IU hCG (eCG + hCG). There was greater ovarian follicular growth in the groups treated with gonadotropins, compared to the control, and there were greater progesterone concentrations in the eCG + hCG group on D9 (P < 0.05). In Experiment 2, 66 ewe lambs were assigned to the same treatment groups described for Experiment 1, and subsequently there was natural mating with rams. There was a greater rate of behavioral estrous manifestation in the eCG (88.5 %; 23/26) and eCG+hCG (85.2 %; 23/27), than control (30.8 %; 4/13; P < 0.05) group. Pregnancy rate was also greater in the eCG (34.6 %; 9/26) and eCG+hCG (18.6 %; 5/27) than control (0 %; 0/13; P < 0.05) group, whereas conception rate, considering only ewe lambs that were mated, was only greater in the eCG group. Although there were greater progesterone concentrations 9 days after treatment in the eCG+hCG group, there was no difference in follicular growth in anestrous ewes, nor was there an effect on estrous behavior manifestation and pregnancy rates in ewe lambs, compared to treatment with only eCG.
Assuntos
Gonadotropina Coriônica/classificação , Gonadotropina Coriônica/farmacologia , Ciclo Estral/efeitos dos fármacos , Fertilidade/efeitos dos fármacos , Folículo Ovariano/efeitos dos fármacos , Ovinos/fisiologia , Animais , Sincronização do Estro , Feminino , Humanos , Acetato de Medroxiprogesterona/administração & dosagem , Estações do AnoRESUMO
The aim of this study was to evaluate the effect of eCG or hCG on the final growth of the dominant follicle in Nelore (Bos indicus) cows submitted to fixed-time AI (FTAI). Eighty-four lactating cows with body condition score (BCS) of 2.9 (range 1-5) were used. At a random day of the estrous cycle (D0) cows received 2â¯mg estradiol benzoate and a reused intravaginal progesterone device (1.9â¯g). At D8, when the device was removed, 0.5â¯mg cloprostenol and 1â¯mg estradiol cypionate was given i.m., and cows were randomly assigned to receive on D8 one of the following treatments: Control (no treatment; nâ¯=â¯17), eCG (300 IU i.m.; nâ¯=â¯17), hCG 300 (300 IU i.m.; nâ¯=â¯18), hCG 200 IM (200 IU i.m.; nâ¯=â¯16) and hCG 200 SC (200 IU s.c.; nâ¯=â¯16). On the same day and 2 days later, cows were subjected to ovarian ultrasonography to evaluate the diameter of the largest follicle and to calculate follicular growth rate (D8 to D10). No differences were observed for the diameter of the largest follicle on D8 (Pâ¯=â¯0.3) or D10 (Pâ¯=â¯0.4) among treatments. However, the growth rate of the dominant follicle between D8 and D10 was greater for the groups eCG and hCG 300 and there were no differences between the other treatments (Controlâ¯=â¯1.1â¯mm/day; eCGâ¯=â¯1.8â¯mm/day; hCG 300â¯=â¯1.8â¯mm/day; hCG 200 IMâ¯=â¯1.3â¯mm/day; hCG 200 SCâ¯=â¯1.3â¯mm/day; Pâ¯=â¯0.02). In addition, more cows from the Group hCG 300 presented premature ovulation (44.4%) than cows from Control (5.8%), eCG (0%), or hCG 200 IM (12.5%), but did not differ from Group hCG 200 SC (18.7%). Regardless of treatment, the size of the largest follicle on D8 was different between cows that presented premature ovulation vs. cows that did not ovulate prematurely (11.3â¯mm vs. 9.9â¯mm, respectively; Pâ¯=â¯0.01). Treatment with different hCG doses on D8 of a FTAI protocol failed to produce similar effects compared to eCG in terms of final follicular growth support and greater ovulatory follicle size. In addition, the groups hCG 300 and hCG 200 SC induced premature ovulation in a greater portion of cows. Thus, a single administration of hCG on D8 does not appear to be a reliable alternative to eCG treatment in FTAI protocols.