Efficiency evaluation of precise ovulation synchronization using progesterone-based protocol and fixed-time artificial insemination to enhance reproductive performance in female buffalo
Abstract:
The swamp buffalo holds tremendous potential in the livestock sector in Asian and Mediterranean countries. Reproductive management in buffaloes by artificial insemination (Al) increases the rate of genetic improvement and production gains. Timing is significant in the fixed-time Al (FTAI), as it defines the optimal moment for insemination. The aims of this research were 1) to investigate ovarian follicular dynamics and timing of ovulation in Thai swamp buffaloes and 2) to compare pregnancy rate in buffaloes submitted to the 11-day progesterone (P4)-prostaglandin Fa (PGF-a)-equine chorionic gonadotrophin (eCG)-gonadotropin-releasing hormone (GnRH)-based protocol with different timing of insemination. This study was divided into two experiments following the objectives. In experiment 1, ovarian follicular dynamics and timing of ovulation were determined from 30 buffaloes receiving P4 device insert from Days 0 to 11, PGF, and eCG on Day iversi 11, and GnRH at 48 h after P4 device removal. Ovaries were evaluated using ultrasonography with a real-time brightness-mode (B-mode) at Days 0, 2, 4, 6, 8, 10, and 11 and at 24 to 192 h after CIDR withdrawal. The size and position of dominant follicle (DF) were recorded and sketched on the ovarian charts to analyze the pattern of growth and establish follicular growth rate. To verify the occurrence of ovulation, the buffaloes were monitored by means of a transrectal ultrasonography twice a day to determine the largest follicle (LF), at 72 h after CIDR removal until ovulation occurred. Based on the detection of ovulation occurrence, a total of 30 female buffaloes was divided into two groups as follows: ovulatory (n = 20) and anovulatory (n = 10) groups. Ovulatory buffaloes had greater (P = 0.004) growth rate of the DF from Day 11 to 48 h after P4 device withdrawal compared with anovulatory buffaloes (1.2±0.10 mm/day vs. 0.8 ± 0.11 mm/day). Ovulatory buffaloes had greater vascular index of the LF (8.3 ± 1.50% vs. 5.3±0.68% ; P = 0.043 ) and the proportion of superficial cells in vaginal smears (47.2 ± 1.8% vs. 29.53.5% ; P = 0.004 ) ; 24 h after the end of the completion of ovulation-synchronization (on Day 14), compared with anovulatory buffaloes. The interval between CIDR removal and ovulation was 100.8±4.72 h and ranged from 72 to 180 h in ovulatory buffaloes. Moreover, the most common timing of ovulation was being 96 h (75.0%) and 120 h (20.0%) after CIDR withdrawal. Based on the distribution and percentage of buffaloes ovulating after CIDR removal (from experiment 1), 75.0% and 10.0% of the buffaloes ovulated 96 h and 120 h after CIDR removal, respectively. Thus, the first timing of the FIAI was designated as 72 h (24 h before ovulation at 96 h after CIDR removal) after CIDR withdrawal (FTAI-72 h). The second timing of the FTAI was designated as 96 h (24 h before ovulation at 120 h after CIDR removal) after CIDR withdrawal (FTAI-96 h). In experiment 2, pregnancy rate was compared between buffaloes that inseminated either at 72 h (n = 35) , 96 h (n =27) after P4 device removal. Inseminating buffaloes 72 h (71.4%) after P4 device removal yielded more pregnancy rate than when buffaloes were inseminated 96 h (44.4%) after P4 device removal (P 0.033). Moreover, the likelihood of pregnancy increased (P = 0.035) 3.12 times in buffaloes with a greater size of the LF (> 9.7 mm) on the day of the FTAI. It is concluded that optimal pregnancy rate can be achieved when Thai swamp buffaloes are bred artificially 72 h after P4 device removal following ovulation-synchronization with the 11-day P4-PGF a-eCG-GnRH-based with the P4-PGF-a-eCG protocol.