Heidari F, Dirandeh E, Ansari Pirsaraei Z, Colazo M G
1Department of Animal Science,Sari Agricultural Sciences and Natural Resources University,PO Box 578,Sari,Mazandaran,Iran.
2Livestock Research Section,Alberta Agriculture and Forestry,Edmonton,AB,Canada,T6H 5T6.
Animal. 2017 Nov;11(11):2002-2009. doi: 10.1017/S1751731117000520. Epub 2017 Mar 15.
In dairy cows, subjected to a G6G protocol, objectives were to determine effects of (1) extending the interval from prostaglandin F2α (PGF2α) to gonadotropin-releasing hormone (GnRH) during presynchronization; and (2) adding a second PGF2α treatment before artificial insemination (AI), on ovarian response, plasma progesterone (P4) concentrations and pregnancy per AI (P/AI). In a 2×2 factorial design, lactating cows were randomly assigned to one of four timed AI (TAI) protocols: (1) G6G (n=149), one injection of PGF2α, GnRH 2 days later and a 7-day Ovsynch (GnRH, 7 days, PGF2α, 56 h, GnRH, 16 h, TAI) was initiated 6 days later; (2) G6GP (n=144), an additional PGF2α treatment (24 h after the first) during Ovsynch of the G6G protocol; (3) MG6G, one injection of PGF2α, GnRH 4 days later before initiation of the G6G protocol; and (4) MG6GP, an additional PGF2α treatment (24 h after the first) during Ovsynch of the MG6G protocol. Blood samples were collected (subset of 200 cows) at first GnRH and PGF2α of the Ovsynch, and at TAI to measure P4. Ultrasound examinations were performed in a subset of 406 cows to evaluate ovarian response at various times of Ovsynch, and in all cattle to determine pregnancy status at 32 and 60 days after TAI. Extending the interval by 2 days between PGF2α and GnRH during presynchronization increased (P<0.01) ovulatory response to first GnRH of Ovsynch, circulating P4 during Ovsynch, and P/AI at 32 and 60 days after TAI. Adding a second PGF2α treatment before AI increased the proportion of cows with luteal regression (P=0.04), improved P/AI at 60 days after TAI (P=0.05), and reduced pregnancy loss between 30 and 60 days after TAI (P=0.04). In summary, extending the interval from PGF2α to GnRH during presynchronization increased response to first GnRH of Ovsynch and P4 concentrations during Ovsynch, whereas adding a second PGF2α treatment before AI enhanced luteal regression. Both modifications of the G6G protocol improved fertility in lactating dairy cows.
在接受G6G方案的奶牛中，目标是确定：（1）在预同步期间延长从前列腺素F2α（PGF2α）至促性腺激素释放激素（GnRH）的间隔时间；以及（2）在人工授精（AI）前添加第二次PGF2α处理，对卵巢反应、血浆孕酮（P4）浓度和每次AI的妊娠率（P/AI）的影响。采用2×2析因设计，将泌乳奶牛随机分配至四种定时AI（TAI）方案之一：（1）G6G（n = 149），注射一次PGF2α，2天后注射GnRH，6天后启动7天的同期发情程序（GnRH，7天，PGF2α，56小时，GnRH，16小时，TAI）；（2）G6GP（n = 144），在G6G方案的同期发情程序中（第一次注射后24小时）额外进行一次PGF2α处理；（3）MG6G，注射一次PGF2α，在启动G6G方案前4天注射GnRH；（4）MG6GP，在MG6G方案的同期发情程序中（第一次注射后24小时）额外进行一次PGF2α处理。在同期发情程序的第一次GnRH和PGF2α时以及TAI时采集血样（200头奶牛的子集）以测定P4。对406头奶牛的子集进行超声检查，以评估同期发情程序不同时间的卵巢反应，并对所有奶牛进行检查以确定TAI后32天和60天的妊娠状态。在预同步期间将PGF2α与GnRH之间的间隔延长2天，可增加（P<0.01）对同期发情程序第一次GnRH的排卵反应、同期发情期间的循环P4以及TAI后32天和60天的P/AI。在AI前添加第二次PGF2α处理可增加黄体退化奶牛的比例（P = 0.04），改善TAI后60天的P/AI（P = 0.05），并减少TAI后30至60天的妊娠损失（P = 0.04）。总之，在预同步期间延长从PGF2α至GnRH的间隔时间可增加对同期发情程序第一次GnRH的反应以及同期发情期间的P4浓度，而在AI前添加第二次PGF2α处理可增强黄体退化。G6G方案的这两种修改均提高了泌乳奶牛的繁殖力。
