Ayres H, Martins C M, Ferreira R M, Mello J E, Dominguez J H, Souza A H, Valentin R, Santos I C C, Baruselli P S
Departamento de Reprodução Animal, FMVZ-USP, Rua Prof. Orlando Marques de Paiva 87, CEP 05508-000, São Paulo, SP, Brazil.
Anim Reprod Sci. 2008 Dec;109(1-4):77-87. doi: 10.1016/j.anireprosci.2007.12.001. Epub 2007 Dec 23.
The present study investigated how the timing of the administration of estradiol benzoate (EB) impacted the synchronization of ovulation in fixed-time artificial insemination protocols of cattle. To accomplish this, two experiments were conducted, with EB injection occurring at different times: at withdrawal of the progesterone-releasing (P4) intravaginal device or 24h later. The effectiveness of these times was compared by examining ovarian follicular dynamics (Experiment 1, n=30) and conception rates (Experiment 2, n=504). In Experiment 1, follicular dynamics was performed in 30 Nelore cows (Bos indicus) allocated into two groups. On a random day of the estrous cycle (Day 0), both groups received 2mg of EB i.m. and a P4-releasing intravaginal device, which was removed on Day 8, when 400 IU of eCG and 150 microg of PGF were administered. The control group (G-EB9; n=15) received 1mg of EB on Day 9, while Group EB8 (G-EB8; n=15) received the same dose a day earlier. Ovarian ultrasonographic evaluations were performed every 8h after device removal until ovulation. The timing of EB administration (Day 8 compared with Day 9) did affect the interval between P4 device removal to ovulation (59.4+/-2.0 h compared with 69.3+/-1.7h) and maximum diameter of dominant (1.54+/-0.06 acm compared with 1.71+/-0.05 bcm, P=0.03) and ovulatory (1.46+/-0.05 acm compared with 1.58+/-0.04 bcm, P<0.01) follicles. In Experiment 2, 504 suckling cows received the same treatment described in Experiment 1, but insemination was performed as follows: Group EB8-AI48 h (G-EB8-AI48 h; n=119) and Group EB8-AI54 h (G-EB8-AI54 h; n=134) received 1mg of EB on Day 8 and FTAI was performed, respectively, 48 or 54 h after P4 device removal. Group EB9-AI48h (G-EB9-AI48 h; n=126) and Group EB9-AI54 h (G-EB9-AI54 h; n=125) received the same treatments and underwent the same FTAI protocols as G-EB8-AI48 h and G-EB8-AI54 h, respectively; however, EB was administered on Day 9. Conception rates were greater (P<0.05) in G-EB9-AI54 h [63.2% (79/125) a], G-EB9-AI48 h [58.7% (74/126) a] and G-EB8-AI48 h [58.8% (70/119) a] than in G-EB8-AI54 h [34.3% (46/134) b]. We concluded that when EB administration occurred at device withdrawal (D8), the interval to ovulation shortened and dominant and ovulatory follicle diameters decreased. Furthermore, when EB treatment was performed 24h after device removal, FTAI conducted at either 48 or 54 h resulted in similar conception rates. However, EB treatment on the same day as device withdrawal resulted in a lesser conception rate when FTAI was conducted 54 h after device removal.
本研究调查了苯甲酸雌二醇（EB）的给药时间如何影响牛定时人工授精方案中排卵的同步性。为此，进行了两项实验，EB注射在不同时间进行：在取出释放孕酮（P4）的阴道内装置时或24小时后。通过检查卵巢卵泡动态（实验1，n = 30）和受孕率（实验2，n = 504）来比较这些时间的有效性。在实验1中，对30头内洛尔牛（印度牛）进行卵泡动态研究，将其分为两组。在发情周期的随机一天（第0天），两组均肌肉注射2mg EB并放置一个释放P4的阴道内装置，该装置在第8天取出，此时给予400IU的eCG和150μg的PGF。对照组（G-EB9；n = 15）在第9天接受1mg EB，而EB8组（G-EB8；n = 15）提前一天接受相同剂量。在取出装置后每8小时进行一次卵巢超声检查，直至排卵。EB给药时间（第8天与第9天相比）确实影响了从取出P4装置到排卵的间隔时间（分别为59.4±2.0小时和69.3±1.7小时）以及优势卵泡（分别为1.54±0.06acm和1.71±0.05bcm，P = 0.03）和排卵卵泡（分别为1.46±0.05acm和1.58±0.04bcm，P<0.01）的最大直径。在实验2中，504头哺乳母牛接受了与实验1相同的处理，但授精如下：EB8-AI48小时组（G-EB8-AI48 h；n = 119）和EB8-AI54小时组（G-EB8-AI54 h；n = 134）在第8天接受1mg EB，并分别在取出P4装置后48或54小时进行定时人工授精。EB9-AI48小时组（G-EB9-AI48 h；n = 126）和EB9-AI54小时组（G-EB9-AI54 h；n = 125）分别接受与G-EB8-AI48 h和G-EB8-AI54 h相同的处理并进行相同的定时人工授精方案；然而，EB在第9天给药。G-EB9-AI54小时组[63.2%（79/125）a]、G-EB9-AI48小时组[58.7%（74/126）a]和G-EB8-AI48小时组[58.8%（70/119）a]的受孕率高于G-EB8-AI54小时组[34.3%（46/134）b]（P<0.05）。我们得出结论，当在取出装置时（第8天）给予EB时，排卵间隔缩短，优势卵泡和排卵卵泡直径减小。此外，当在取出装置24小时后进行EB处理时，在48或54小时进行定时人工授精产生的受孕率相似。然而，当在取出装置后54小时进行定时人工授精时，在取出装置当天进行EB处理导致受孕率较低。
