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Aim of this study was to determine the effect of double-Ovsynch (DO) and presynchronization (PS) protocols on ovarian follicular dynamics, progesterone (P4) concentration and pregnancy rate at first postpartum AI in Friesian cows. Total of 44 lactating cows on 39-45 day post-partum (12 primiparous and 32 multiparous cows) were used in this study. Cows were divided into two similar groups (22 cows in each). Cows in G1 were pre-synchronized by two PGF2α (Estrumate) injections at 14 d interval (on days 42 and 56±3 post-partum), then initiate the Ovsynch-timed AI protocol after 12 days. Cows in G2 were injected on day 0 with 1 dose of GnRH (Receptal) on day 51±3 post-partum, with PGF2α on day 7 and 2 dose of GnRH after 72 h, then initiate the Ovsynch-timed AI protocol after 7 days. Cows in both groups were treated with the same Ovsynch protocol: 1 GnRH on days 68±3 postpartum, PGF2α after 7 days, 2 GnRH 56 h after PGF2α, and timed AI after 16 h. Cows were subjected to ultrasonography device to examine follicular number (FN) and diameter of dominant follicles (DF) as well as counting the number of corpora lutea (NCLs). Blood samples were collected to determine P4 in blood serum. Results showed that FN or NCLs/ovary on day 0 or during pre-synchronization treatment was not affected significantly by treatment. FN/ovary at 2 GnRH of Ovsynch-breeding protocol was greater in G1 than in G2 (1.6 vs. 2.0 foll./ovary). However, NCLs and DF diameter during Ovsynch-breeding in G1 and G2 were not affected significantly by treatment. Concentration of P4 in blood serum of cows on days 0, pre-synch, 1 GnRH and PGF2 injections was not affected significantly by treatment. On day of 2 GnRH injection, P4 concentration was higher (P<0.01) in G2 than in G1. Concentration of P4 was slightly higher (P>0.05) in pregnant than in non-pregnant cows during pre-synch protocol. Progesterone concentration on day 75 showed an opposite trend, being lower (P<0.05) in pregnant than in non-pregnant cows. Ovulation rate to 1 GnRH injection was insignificantly higher in G2 (88.9%) than in G1 (82.4%). While, pregnancy rate based on total number of treated and ovulated cows was insignificantly higher in G1 (45.5 and 71.4%) than in G2 (36.4 and 50.0%), respectively. Higher pregnancy rates was in association with higher P4 concentration (>3 ng/ml) on day 0 and at 1 GnRH of Ovsynch breeding protocol and lower P4 concentration (<1 ng/ml) at 2 GnRH. Thus, pre-synchronization with PresynchOvsynch increased cyclicity and fertility of Frisian cows at first service postpartum in Frisian cows. However, Double-Ovsynch gave higher ovulation rate than presynchOvsynch.

journal of animal and poultry production

EFFECT OF DOUBLE OR PRE-SYNCHRONIZATION OVSYNCH PROTOCOLS ON FOLLICULAR DYNAMICS, PROGESTERONE PROFILE AND FIRST SERVICE PREGNANCY RATE IN TIMED ARTIFICIAL INSEMINATION IN FRIESIAN COWS