Dinâmica folicular de vacas da raça guzerá submetidas a três protocolos de sincronização da ovulação

Abstract

This study aimed to assess the follicular dynamics of Guzerat cows treated with three protocols for synchronization of ovulation where they used vaginal implant impregnated with progesterone or the Ovsynch protocol, besides the use of estradiol benzoate or GnRH to induce ovulation.There were used 18 PO Guzerat cows, multiparous non-lactating, aging between four and seven years, good body score condition, ranging from 3.0 to 4.0, The animals were kept in extensive management, where the diet provided met the nutritional requirements including protein mineral salt and water "ad libitum". The animals were divided into three groups, in group 1 (n = 6) it was applied at the D0, an intravaginal device CIDR® along with 2 mg of estradiol benzoate, at D8 it was administered 300 mg of a prostaglandin analogue and 300 IU of eCG besides intravaginal device removal, at D9 it was administered 1 mg of estradiol benzoate and at D11 artificial insemination was carried out. In group 2 (n = 6) it was used the same protocols as in group 1 except for the induction of ovulation when it was used 17 mg of a GnRH analogue and at D11 artificial insemination was carried. In group 3 (n = 6) was applied at D0, 200 mg of GnRH analogue, 0.530 mg of prostaglandin analogue at D7, at D9 it was administered 100 mg of GnRH analogue and at D10 artificial insemination was carried. From D0 to D8 animals were examined daily (24/24 h) by transrectal ultrasound .After removal of the implant on D8 in groups 1 and 2 and application of prostaglandin D7 (group 3) animals were assessed four times a day (6/6 hours) until D10 of the Protocol. A new follicular wave emergence for groups 1, 2 and 3 was observed respectively, 2.6 ± 0.16; 2.7 ± 0.18 and 2.9 ± 0.16 days, with no statistical difference (P < 0.05) between groups .There was statistical difference for groups 1, 2 and 3 in the range of wave emergence and ovulation in days, 7.1  0.18; 6.37 0.31; 5.33 0.66, the interval between implant removal and ovulation in hours, 64.2 6.99, 61.0 12.36, interval between the application of inducing ovulation and in hours, 43.6 6.89, 41.0 11.25, 38.2 7.89, greatest diameter of the DF (day 8), 10.71 0.30, 9.41 0.24, 9.75 0.35, greatest diameter of the DF (day 10), 13.1 0.23, 11.7 0.22, 12.0 0.34, Average follicle growth until day 8 - (mm / day), 1.36 0.07, 0.92 0.10, 1.10 0.11, Average follicle growth of 8-10 days - (mm / day), 2.40 0.08, 2.28 0.11, 2.23 0.10 and the percentage of animals that ovulated, 83.34% (5/6) , 66.67% (4/6), 50% (3/6). So the protocols of experimental groups 1 and 2 were moreeffective in promoting the synchronization of ovulation and are indicated to be used in a program of fixed-time artificial insemination in Guzerat cows.