Sales J N S, Carvalho J B P, Crepaldi G A, Soares J G, Girotto R W, Maio J R G, Souza J C, Baruselli P S
Department of Animal Reproduction, FMVZ-USP, São Paulo-SP, Brazil; Department of Veterinary Medicine, UFLA, Lavras, Minas Gerais, Brazil.
APTA-Vale do Paraíba Regional Center, Pindamonhangaba, São Paulo, Brazil.
Theriogenology. 2015 Apr 1;83(6):1093-100. doi: 10.1016/j.theriogenology.2014.12.009. Epub 2014 Dec 12.
Four experiments were designed to evaluate the effect of different circulating progesterone (P4) concentrations during a synchronization of ovulation protocol for the timed artificial insemination (TAI) of Bos indicus (Nelore) beef cattle. In the first trial, 13 ovariectomized Nelore heifers were randomly allocated into one of three groups using new P4 devices (New; 1.0 g P4), previously used P4 devices for 8 days (Used1x), and previously used P4 devices for 16 days (Used2x), in a crossover experimental design. The circulating P4 concentrations during the P4 device treatment were lower for Used1x (2.3 ± 0.1 ng/mL) and Used2x (2.0 ± 0.1 ng/mL) than those for New (3.8 ± 0.2 ng/mL; P = 0.001). In the second trial, the ovarian follicular dynamics of 60 anestrous cows were evaluated after the cows received the treatments described previously (New [n = 20], Used1x [n = 20], and Used2x [n = 20]). During the insertion of the P4 device, the cows were administered 2.0-mg estradiol benzoate. Eight days later, the P4 device was removed, and the cows were administered 0.53-mg sodium cloprostenol, 300 IU eCG, and 1-mg estradiol cypionate. There were no differences among the groups during the interval from P4 device removal to ovulation (73.7 ± 2.9 vs. 69.8 ± 2.4 vs. 68.4 ± 2.3 hours) or regarding the ovulation rate (70.0% vs. 80.0% vs. 85.0%). However, the maximum diameter of the largest follicle was greater (P = 0.06) in the Used2x (15.3 ± 0.4 mm) than that of New (13.5 ± 0.8 mm) and Used1x (14.9 ± 0.5 mm). In experiment 3, 443 anestrous cows were randomly assigned into one of the three treatments (New [n = 144] vs. Used1x [n = 167] vs. Used2x [n = 132]) and received a TAI 48 hours after the P4 device removal. The diameter of the largest follicle during the device removal (10.7 ± 0.3 vs. 11.2 ± 0.2 vs. 11.3 ± 0.3 mm) and the 30-day pregnancy rates (51.4% vs. 53.9% vs. 43.2%) did not differ among the experimental groups. In experiment 4, a field trial with 593 B indicus (Nelore) cows was conducted to evaluate the pregnancy per AI using different levels of P4 in a TAI protocol (New [n = 189] vs. Used1x [n = 203] vs. Used2x [n = 201]). The pregnancy per AI was similar between the treatment groups (63.5% vs. 57.6% vs. 62.7%). In conclusion, the low circulating P4 concentrations that were released from a used P4 device efficiently controlled the ovarian follicular growth and exhibited no detrimental effects on the pregnancy rates of the B indicus (Nelore) beef cattle.
设计了四项实验，以评估在印度瘤牛（Nelore）肉牛定时人工授精（TAI）的排卵同步方案中，不同循环孕酮（P4）浓度的影响。在第一项试验中，采用交叉实验设计，将13头去卵巢的Nelore小母牛随机分为三组，分别使用新的P4装置（New；1.0 g P4）、先前使用过8天的P4装置（Used1x）和先前使用过16天的P4装置（Used2x）。在P4装置处理期间，Used1x组（2.3±0.1 ng/mL）和Used2x组（2.0±0.1 ng/mL）的循环P4浓度低于New组（3.8±0.2 ng/mL；P = 0.001）。在第二项试验中，对60头处于乏情期的母牛进行了卵巢卵泡动态评估，这些母牛接受了先前描述的处理（New组[n = 20]、Used1x组[n = 20]和Used2x组[n = 20]）。在插入P4装置时，给母牛注射2.0 mg苯甲酸雌二醇。八天后，取出P4装置，并给母牛注射0.53 mg氯前列醇钠、300 IU eCG和1 mg环丙孕酮。在从取出P4装置到排卵的间隔时间（73.7±2.9小时对69.8±2.4小时对68.4±2.3小时）或排卵率（70.0%对80.0%对85.0%）方面，各组之间没有差异。然而，Used2x组（15.3±0.4 mm）最大卵泡的最大直径大于New组（13.5±0.8 mm）和Used1x组（14.9±0.5 mm）（P = 0.06）。在实验3中，将443头乏情期母牛随机分为三种处理之一（New组[n = 144]对Used1x组[n = 167]对Used2x组[n = 132]），并在取出P4装置后48小时进行TAI。在取出装置时最大卵泡的直径（10.7±0.3 mm对11.2±0.2 mm对11.3±0.3 mm）和30天妊娠率（51.4%对53.9%对43.2%）在各实验组之间没有差异。在实验4中，对593头印度瘤牛（Nelore）母牛进行了田间试验，以评估在TAI方案中使用不同水平的P4时每次人工授精后的妊娠情况（New组[n = 189]对Used1x组[n = 203]对Used2x组[n = 201]）。各处理组之间每次人工授精后的妊娠情况相似（63.5%对57.6%对62.7%）。总之，从用过的P4装置释放的低循环P4浓度有效地控制了卵巢卵泡的生长，并且对印度瘤牛（Nelore）肉牛的妊娠率没有不利影响。
