Abstract：
The objective of this study was to evaluate the impact of early progesterone removal on pregnancy rates to fixed-time artificial insemination (FTAI) in presynchronized beef cows. Postpartum beef cows (n = 882) were randomly assigned to 1 of 2 treatments: 1) 7&7 Synch: cows received a controlled internal drug release insert (CIDR) and a 25-mg injection of prostaglandin F2α on day 0, 100 μg of GnRH on day 7, a second injection of prostaglandin F2α (PG2) at CIDR removal on day 14, and a second injection of GnRH at FTAI 60-66 h after PG2 (day 17); 2) 7&6 Synch: cows received the same treatment as 7&7 Synch; however, CIDR removal occurred in conjunction with PG2 on day 13, while FTAI remained at 60-66 h after CIDR removal (day 16). Ovarian ultrasonography was performed to determine follicle diameter at PG2 and FTAI in a subset of cows (n = 40). Cows exposed to the 7&7 Synch tended to have larger follicle diameter at PG2 compared with 7&6 Synch cows (P = 0.09); however, there were no differences in follicle diameter at FTAI. No differences were determined between treatments for the expression of estrus (7&7 Synch: 61.6 ± 5.30; 7&6 Synch: 54.1 ± 5.45; P = 0.31) or pregnancy rates to FTAI (7&7 Synch: 60.8 ± 3.83; 7&6 Synch: 57.0 ± 3.84; P = 0.42). In conclusion, early removal of progesterone did not impact pregnancy rates in presynchronized beef cows.
摘要：
这项研究的目的是评估早期去除孕酮对预同步肉牛固定时间人工授精（FTAI）妊娠率的影响。产后肉牛（n=882）被随机分配到2种治疗方法中的1种：1）7和7同步：母牛在第0天接受了受控的内部药物释放插入物（CIDR）和25mg的前列腺素F2α注射，第7天100μg的GnRH，在第14天接受了CIDR去除的第二次注射前列腺素F2α（PnRH），第7天接受了Gn66和CIDR去除在第13天与PG2一起发生，而FTAI在CIDR去除后60-66小时保持（第16天）。进行卵巢超声检查以确定一部分母牛（n=40）中PG2和FTAI的卵泡直径。与7和6Synch奶牛相比，暴露于7和7Synch的奶牛在PG2时倾向于具有更大的卵泡直径（P=0.09）；然而，FTAI时卵泡直径无差异。在发情期(7&7Synch:61.6±5.30;7&6Synch:54.1±5.45;P=0.31)的表达或FTAI的妊娠率(7&7Synch:60.8±3.83;7&6Synch:57.0±3.84;P=0.42)的处理之间没有差异。总之,孕酮的早期去除并不影响同步前肉牛的妊娠率.
