Synchronized ovulation with gonadotropin-releasing hormone, prostaglandin F and fixed-time insemination

摘要

SummaryLactating Holstein cows and replacementheifers were treated with a novel synchronizedovulation protocol, which involves one fixedtimeinsemination without heat detection. Oneinjection of GnRH (Cystorelin®) was given,followed in 7 days with an injection of PGF2a(Lutalyse®). Approximately 32 to 36 hr later,ovulation was induced with a second injectionof GnRH, and one fixed-time insemination wasgiven 18 hr later. Control cattle were given oneinjection of PGF and inseminated at observed 2aestrus. Pregnancy rates measured by palpationbetween 38 and 52 days after insemination incontrols (47.1%) were slightly, but not significantly,greater than those in the synchronizedovulation treatment (35.3%). Thetreatment worked much better in lactating cowsthan in virgin heifers. This treatment may beparticularly well suited to cows in which estrusis rarely observed, as well as for synchronizingfirst or repeat services.