Seasonal effects on luteal activity during post partum were evaluated in two consecutive studies in 253 dairy cows in Northern Italy. In study 1, plasma progesterone concentrations were determined on days 14, 21, 28, 35, 42, 49 and 56 post partum and in study 2 cows were synchronized and inseminated at a fixed time using two regimes based on the 'Ovsynch' protocol. Study 1: Animals were classif...

We hypothesized that 50mg of prostaglandin F2α (PG) on d 6 would induce luteolysis in a traditional 5-d Ovsynch-72 program [GnRH 5 d before (d 0) and 72 h after (d 8) 25-mg PG doses (d 5 and 6 after GnRH); timed artificial insemination (AI) on d 8]. Experiment 1 monitored luteal regression of original and GnRH-induced luteal tissue (corpus luteum, CL) by transrectal ultrasonography and blood se...

Experiments were designed to investigate the effect of different doses and timing of an eCG treatment given during GnRH-based synchronization protocols on follicular dynamics and fertility in cattle. In Exp. 1, Angus heifers (n = 50) received a 7-d Ovsynch + progesterone protocol (on d 0, GnRH and progesterone insert were administered; on d 7, progesterone insert was removed and PGF2α was injec...

Our objective was to evaluate the effect of a progesterone-releasing intravaginal device (PRID) in 7-d Ovsynch protocol on pregnancy per artificial insemination (P/AI) and loss, compared with standard without progesterone supplementation. We hypothesized that supplementation during an would increase P/AI decrease loss. Data were collected lactating Holstein cows (n = 716) either received (contr...

Experiment 1 evaluated pregnancy rates (PRs) when estradiol cypionate (ECP) replaced the second GnRH injection of a timed artificial insemination (TAI) protocol for lactating dairy cows. Cows were pre-synchronized with two injections of PGF2α (Lutalyse r , Pharmacia Corp., 25 mg; i.m.) given to multiparous cows (n=170) at 40 ± 3 and 54 ± 3 d postpartum (dpp) and to primiparous cows (n=201) at 6...