Fertility after synchronization of estrus in dairy heifers using GnRH, PGF2α, and Progesterone (CIDR)

摘要

Our objective was to determine fertilityof heifers after synchronization of estrususing PGF2", preceded by progesterone,GnRH, or both. Dairy heifers (n = 246) wereassigned randomly to three treatments: 1) 50:g of GnRH given 6 d before 25 mg of PGF2(d –1) plus a used intravaginal progesteronereleasinginsert (CIDR-B; d –7 to 0;CIDR+GnRH); 2) same as CIDR+GnRHwithout the GnRH (CIDR); and 3) same asCIDR+GnRH without the used CIDR(GnRH). All heifers were fitted with Heat-Watch® patches and characteristics of estrusexamined before AI included duration ofestrus, number of standing events, and totalduration of standing events. In addition, allheifers were observed visually twice dailyfor estrus. Rates of conception and pregnancydiffered among treatments. All of theestrus-synchronization treatments producedacceptable estrus detection and pregnancyrates but the CIDR+PGF2" treatment wasmost effective for improving conception andpregnancy rates.