dos Santos Ricarda Maria, Goissis Marcelo Demarchi, Fantini David Augusto, Bertan Claudia Maria, Vasconcelos José Luiz Moraes, Binelli Mario
Escola Agrotécnica Federal, Uberlândia, MG, Brazil.
Anim Reprod Sci. 2009 Aug;114(1-3):62-71. doi: 10.1016/j.anireprosci.2008.09.016. Epub 2008 Oct 1.
The objective was to evaluate the influence of varying plasma progesterone (P(4)) concentrations throughout the luteal phase in dairy cows on PGF(2alpha) production (assessed as plasma concentrations of 13,14-dihydro-15-keto-PGF(2alpha); PGFM) following treatment with estradiol-17beta (E(2)) or oxytocin (OT). In all experiments, time of ovulations was synchronized with the OvSynch protocol and Day 0 corresponded to day of second GnRH injection. In Experiment 1, non-lactating dairy cows on Day 6 remained non-treated (n=9), received 20mg LH (n=7), or had ovarian follicles larger than 6mm aspirated (n=8). In Experiment 2, cows on Day 6 were untreated (n=9) or received 5000 IU hCG (n=10). In Experiments 1 and 2, all cows received 3mg E(2) on Day 17, and blood samples were collected every 30 min from 2h before to 10h after E(2). Experiment 3 was conducted in two periods, each from Days 0 to 17 of the estrous cycle. At the end of Period 1, animals switched treatments in a crossover arrangement. Animals in Group 2/8 (n=4) received 2 kg/d of concentrate in the first period and 8 kg/d in the second period. Animals in Group 8/2 (n=7) received the alternate sequence. Blood was collected daily for measurement of P(4) 4h after concentrate feeding. On Day 17, blood was collected from 1h before to 1h after a 100 IU OT injection. In Experiment 1, both plasma P(4) and release of PGF(2alpha) were similar between LH-treated and control cows (P>0.10). In Experiment 2, plasma P(4) was elevated to a greater extent on Day 17 in cows treated with hCG (P<0.05) and plasma PGFM was also greater in hCG-treated animals (treatment x time interaction; P<0.05). In Experiment 3, there was a group x period interaction (P<0.01) for plasma P(4), indicating that less concentrate feeding was associated with greater plasma P(4). Release of PGF(2alpha) in response to OT was greater for cows receiving less concentrate (group x period interaction; P<0.05). In conclusion, dairy cows with more elevated blood P(4) concentrations released more PGF(2alpha) in response to E(2) or OT.
目的是评估奶牛黄体期血浆孕酮（P(4)）浓度变化对用雌二醇-17β（E(2)）或催产素（OT）处理后PGF(2α)产生（以13,14-二氢-15-酮-PGF(2α)；PGFM的血浆浓度评估）的影响。在所有实验中，排卵时间通过同期发情方案同步，第0天对应第二次GnRH注射日。在实验1中，第6天的非泌乳奶牛未接受处理（n = 9）、接受20mg促黄体生成素（LH）（n = 7）或抽吸直径大于6mm的卵巢卵泡（n = 8）。在实验2中，第6天的奶牛未接受处理（n = 9）或接受5000IU人绒毛膜促性腺激素（hCG）（n = 10）。在实验1和2中，所有奶牛在第17天接受3mg E(2)，并在E(2)注射前2小时至注射后10小时每30分钟采集一次血样。实验3分两个阶段进行，每个阶段从发情周期的第0天至第17天。在第1阶段结束时，动物以交叉方式更换处理。第2/8组（n = 4）的动物在第一阶段接受2kg/d的精饲料，在第二阶段接受8kg/d。第8/2组（n = 7）的动物接受相反的顺序。每天在精饲料投喂后4小时采集血液以测定P(4)。在第17天，在注射100IU OT前1小时至注射后1小时采集血液。在实验1中，LH处理的奶牛与对照奶牛的血浆P(4)和PGF(2α)释放相似（P>0.10）。在实验2中，hCG处理的奶牛在第17天血浆P(4)升高幅度更大（P<0.05），hCG处理的动物血浆PGFM也更高（处理×时间交互作用；P<0.05）。在实验3中，血浆P(4)存在组×阶段交互作用（P<0.01），表明精饲料投喂量越少，血浆P(4)越高。接受较少精饲料的奶牛对OT刺激的PGF(2α)释放更大（组×阶段交互作用；P<0.05）。总之，血液P(4)浓度较高的奶牛对E(2)或OT刺激释放更多的PGF(2α)。
