Fishman-Holland Heidi, Stoskute Agne, Ferrer Maria S, Veal Deana, Bittar Joao H J, Rollin Emmanuel, Lourenço Jeferson, Palomares Roberto A
Department of Large Animal Medicine, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA.
Department of Population Health, College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA.
Vet Med Sci. 2019 Aug;5(3):379-389. doi: 10.1002/vms3.171. Epub 2019 Apr 22.
The use of 4-day CoSynch + Controlled internal drug release (CIDR) + timed artificial insemination (TAI) in dairy heifers has resulted in adequate pregnancy rates compared with the 5-day CoSynch + CIDR + TAI protocol. The objective of this study was to compare follicular growth, timing of ovulation and serum progesterone (P ), estradiol (E ) and luteinizing hormone (LH) concentrations in dairy heifers treated with modified 4- or 5-day CoSynch + CIDR protocols (CIDR for 4 or 5 days, PGF α at CIDR removal and GnRH + TAI 72 h later). Twelve cycling Holstein heifers were randomly assigned to either the 4- or 5-day Co-Synch+CIDR (n = 6/treatment) to receive an intravaginal insert CIDR containing 1.38 g of P for 4 or 5 days, respectively. At CIDR removal, 25 mg of PGF α was injected IM; 72 h after CIDR removal, heifers received 100 μg of GnRH IM and timed artificial insemination (TAI). Follicular growth and timing of ovulation were assessed using transrectal ultrasonography. Blood samples were collected at the time of CIDR insertion and at frequent time points after CIDR removal for determination of P (at TAI), E (every 12 h) and LH (every 6 h during the first and second day and every 2 h on the third day). Heifers in the 4-day group had smaller follicles from CIDR insert removal to ovulation compared with heifers in the 5-day treatment. Five of six heifers (83.3%) in the 4-day treatment ovulated at 90-96 h post CIDR insert removal, whereas most heifers in the 5-day treatment (4/6; 66.6%) ovulated at 84-90 h post CIDR insert withdrawal. Heifers in the 5-day treatment reached greater peak LH concentration between 48 and 72 h after CIDR insert removal and lesser E concentration at TAI than heifers in the 4-day treatment. In conclusion, heifers in the 4-day treatment had smaller follicular diameter at 0, 30, 36, 42 and 48 h after CIDR insert removal, longer interval from CIDR insert removal to ovulation, greater E concentrations at TAI, and lesser peak LH concentration than heifers in the 5-day treatment. These results represent a baseline for further studies to determine if prolonging the interval to TAI by 6 h in the 4-day CoSynch+CIDR would improve pregnancy risk.
与5天的同期发情+控制内部药物释放（CIDR）+定时人工授精（TAI）方案相比，在奶牛小母牛中使用4天的同期发情+CIDR+TAI方案可获得足够的妊娠率。本研究的目的是比较采用改良的4天或5天同期发情+CIDR方案（CIDR放置4天或5天，取出CIDR时注射前列腺素Fα，72小时后注射促性腺激素释放激素（GnRH）+TAI）处理的奶牛小母牛的卵泡生长、排卵时间以及血清孕酮（P）、雌二醇（E）和促黄体生成素（LH）浓度。12头处于发情周期的荷斯坦小母牛被随机分配到4天或5天同期发情+CIDR组（每组n = 6头），分别接受含1.38克孕酮的阴道内植入CIDR，放置4天或5天。取出CIDR时，肌肉注射25毫克前列腺素Fα；取出CIDR 72小时后，小母牛肌肉注射100微克GnRH并进行定时人工授精（TAI）。采用经直肠超声检查评估卵泡生长和排卵时间。在插入CIDR时以及取出CIDR后的多个时间点采集血样，用于测定P（TAI时）、E（每12小时一次）和LH（第一天和第二天每6小时一次，第三天每2小时一次）。与5天处理组的小母牛相比，4天处理组的小母牛从取出CIDR到排卵期间卵泡较小。4天处理组的6头小母牛中有5头（83.3%）在取出CIDR后90 - 96小时排卵，而5天处理组的大多数小母牛（4/6；66.6%）在取出CIDR后84 - 90小时排卵。5天处理组的小母牛在取出CIDR后48至72小时达到更高的LH峰值浓度，且TAI时的E浓度低于4天处理组的小母牛。总之，与5天处理组的小母牛相比，4天处理组的小母牛在取出CIDR后0、30、36、42和48小时卵泡直径较小，从取出CIDR到排卵的间隔时间更长，TAI时E浓度更高，LH峰值浓度更低。这些结果为进一步研究确定在4天同期发情+CIDR方案中将TAI间隔延长6小时是否会提高妊娠风险提供了基线数据。
