Burke C R, Mussard M L, Grum D E, Day M L
Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA.
Anim Reprod Sci. 2001 May 31;66(3-4):161-74. doi: 10.1016/s0378-4320(01)00101-4.
The effect of maturity of the dominant follicle (DF) on the capacity of oestradiol benzoate (ODB) to induce oestrus and ovulation was examined in cattle. In experiment 1, 31 prepubertal heifers each received an intravaginal progesterone insert (IPI) and 1mg ODB i.m./500kg BW (ODB1). Daily ovarian ultrasonography detected emergence of a new follicular wave 3.1+/-0.1 days after ODB1. The IPI was removed when newly emerged DF were "young" (1.3+/-0.1 days after emergence; YDF; n=15) or "mature" (4.2+/-0.1 days; MDF; n=16), and 24h later, heifers received 0.75mg ODB/500kg BW (ODB2; n=16) or no further treatment (NoODB2; n=15). Most of the heifers receiving ODB2 were observed in oestrus (15/16) and ovulated (12/16), as compared to 0/15 and 1/15 in the NoODB2 group, respectively (P<0.01). In experiment 2, 32 heifers received ODB1 on day 6 of the oestrous cycle, and new follicular wave emergence was detected 3.2+/-0.1 days later. Heifers received an injection of prostaglandin-F2alpha (PGF) when the DF was young (1.1+/-0.1 days after emergence; YDF; n=16) or mature (4 days; MDF; n=16), and then ODB2 24h later or no further treatment (NoODB2). The interval from PGF to oestrus was greater (P<0.01) in the YDF-NoODB2 (70+/-3.9h) as compared to MDF-NoODB2 group (57+/-1.8h). Inclusion of ODB2 reduced (P<0.01) this interval to 47.0+/-0.7h without regard to the maturity of the DF (maturityxODB2, P<0.05) and also reduced (P<0.05) the interval to ovulation. In experiment 3, 21 suckling anoestrous cows received an IPI and ODB1 at 29.3+/-1.7 days postpartum. The IPI were removed either 1 day (YDF; n=9) or 3.9+/-0.1 days (MDF; n=9) after emergence of a new follicular wave and every cow received ODB2. Oestrus was subsequently detected in all but one animal. Ovulation of the newly emerged DF was detected within 48h of ODB2 in nine of nine cows of the MDF group, and in four of nine of the YDF group (P<0.05). During the subsequent ovulatory cycle, luteal size and plasma concentrations of progesterone were greater (P<0.01) in the MDF group compared to the YDF group. We conclude that behavioural oestrus is readily induced by 0.75mg ODB i.m./500kg BW. Maturity of the DF appeared to have little influence on the ability of the DF to ovulate in heifers. In contrast, young DF in lactating anoestrous cows were less likely to respond to the ovulatory cue provided, and luteal development was compromised in those that did ovulate.
研究了牛体内优势卵泡（DF）的成熟度对苯甲酸雌二醇（ODB）诱导发情和排卵能力的影响。在实验1中，31头青春期前的小母牛均接受了阴道内孕酮植入物（IPI），并按每500千克体重肌肉注射1毫克ODB（ODB1）。每日进行卵巢超声检查，发现注射ODB1后3.1±0.1天出现新的卵泡波。当新出现的DF处于“年轻”阶段（出现后1.3±0.1天；YDF；n = 15）或“成熟”阶段（4.2±0.1天；MDF；n = 16）时，取出IPI，24小时后，小母牛接受0.75毫克ODB/500千克体重（ODB2；n = 16）或不再接受进一步处理（NoODB2；n = 15）。与NoODB2组分别为0/15和1/15相比，大多数接受ODB2的小母牛出现发情（15/16）并排卵（12/16）（P<0.01）。在实验2中，32头小母牛在发情周期的第6天接受ODB1，3.2±0.1天后检测到新的卵泡波出现。当DF处于年轻阶段（出现后1.1±0.1天；YDF；n = 16）或成熟阶段（4天；MDF；n = 16）时，小母牛接受前列腺素-F2α（PGF）注射，24小时后再接受ODB2或不再接受进一步处理（NoODB2）。与MDF-NoODB2组（57±1.8小时）相比，YDF-NoODB2组（70±3.9小时）从PGF到发情的间隔时间更长（P<0.01）。无论DF的成熟度如何，注射ODB2均可将此间隔时间缩短（P<0.01）至47.0±0.7小时（成熟度×ODB2，P<0.05），同时也缩短了（P<0.05）至排卵的间隔时间。在实验3中，21头哺乳期乏情母牛在产后29.3±1.7天接受IPI和ODB1。新卵泡波出现后1天（YDF；n = 9）或3.9±0.1天（MDF；n = 9）取出IPI，每头母牛均接受ODB2。随后，除1头动物外，所有母牛均检测到发情。MDF组9头母牛中有9头在注射ODB2后48小时内检测到新出现的DF排卵，而YDF组9头中有4头（P<0.05）。在随后的排卵周期中，MDF组的黄体大小和孕酮血浆浓度均高于YDF组（P<0.01）。我们得出结论，按每500千克体重肌肉注射0.75毫克ODB可轻易诱导行为发情。DF的成熟度似乎对小母牛DF的排卵能力影响不大。相比之下，哺乳期乏情母牛中的年轻DF对所提供的排卵信号反应较小，并且那些排卵的母牛黄体发育受到影响。
