Garcia-Winder M, Lewis P E, Inskeep E K
Div. Anim. Vet. Sci., West Virginia University, Morgantown 26506-6108.
J Anim Sci. 1988 Jan;66(1):1-4. doi: 10.2527/jas1988.6611.
The effect of implants of estradiol on initiation of ovarian cycles postpartum was studied in 201 anestrous beef cows. Cows from four farms were used over a 2-yr period in a 2 x 3 factorial arrangement of treatments with estradiol implants and stage postpartum as main effects. Cows were assigned at random within date of calving within farm to receive an ear implant containing estradiol-17 beta (24 mg) for 21 d or to serve as controls. Stages postpartum at implantation were divided into less than or equal to 25, 26 to 39, and greater than or equal to 40 d, three stages that should reflect potential changes in hypothalmic-hypophysial sensitivity to estradiol. Blood samples for determination of progesterone were obtained and rectal examinations of the ovaries performed at implant insertion, 14 d after insertion, at implant removal (d 21), and 14 d after removal (d 35) to assess ovulatory response to treatment. Circulating concentrations of estradiol on d 14 of treatment averaged 3.2 +/- 1.0 and 23.1 +/- 4.7 pg/ml for control and estradiol-treated cows, respectively. Compared with control cows, treatment with estradiol initiated after d 26 postpartum increased the proportion of cows that ovulated during the experimental period. No differences were seen in the average days postpartum when cows were first determined to have ovulated.
在201头产后处于乏情期的肉用母牛中，研究了植入雌二醇对产后卵巢周期启动的影响。在两年时间里，使用了来自四个农场的母牛，采用2×3析因试验设计，将雌二醇植入和产后阶段作为主要效应因素。在每个农场内，根据产犊日期将母牛随机分组，一组接受含有17β-雌二醇（24毫克）的耳部植入物，持续21天，另一组作为对照。植入时的产后阶段分为小于或等于25天、26至39天、大于或等于40天这三个阶段，这三个阶段应能反映下丘脑 - 垂体对雌二醇敏感性的潜在变化。在植入时、植入后14天、取出植入物时（第21天）以及取出后14天（第35天）采集血样测定孕酮，并对卵巢进行直肠检查，以评估对治疗的排卵反应。在治疗第14天时，对照母牛和接受雌二醇治疗的母牛的循环雌二醇浓度平均分别为3.2±1.0和23.1±4.7皮克/毫升。与对照母牛相比，产后第26天之后开始用雌二醇治疗增加了在实验期内排卵的母牛比例。在首次确定母牛排卵时的平均产后天数方面未观察到差异。
