The Influence of the Interval between Administration of PGF2α, in the Pre-Synchronization Treatments (2xPGF2α), in the Ovsynch Synchronization Program of the Oestrus and the Ovulations in Dairy Cows

The results of synchronization of estrus and ovulation by Ovsynch program, can be improved if stages of estrous cycles in cows are synchronized, through two administrations of PGF2α, before the administration the first dose of GnRH. The aim of our paper was to establish if the interval between the administration of two doses of PGF 2α influence the rates of conception/pregnancy after the Ovsynch synchronization program of the estrus and ovulation. The treatments of pre-synchronization with PGF2α were started in the interval postpartum 46-50 days. At the first lot of cows, the interval between two administrations of PGF 2α was 7 days; at the second lot, the interval between the two administrations of PGF 2α was 12 days and at the third lot the interval between two administrations of PGF 2α was 14 days. As a source of PGF2α, we used 2 ml Proliz (I. Pasteur, Bucharest România) (400 mcg Cloprostenol). At all the three groups, we started the Ovsynch program at 7 days after the last administration of PGF2α by administration of 100 mcg GnRH (Ovarelin), after 7 days we administered 400 mcg Cloprostenol, and after 48 hours we administered the last dose of 100 mcg GnRH. All females were inseminated at 16-20 hours after the last dose of GnRH. At the pre-synchronized cows with 2xPGF 2α, at interval of 7 days, the rate of conception was 81.43%, significantly higher (p˂0.05) than at the pre-syncronized cow at 12 or 14 days (71.15%, 71.64% respectively). With regard at the pregnancy rates were 70%, significantly higher (p˂0.05) compared with pre-synchronized cows at 12 or 14 days (55.77%, 56.72% respectively). Are not significant differences (p> 0.05) between the pre-syncrhonized cows at 12 or 14 days.