Souza, Alexandre H.Silva, E.Cunha, Arcelina PachecoGuenther, J. N.Peto, C. M.Caraviello, D. Z.Wiltbank, Milo C.2022-08-112022-08-112007-10Souza, A. H. vd. (2007). "Supplementation with estradiol-17 beta before the last gonadotropin-releasing hormone injection of the ovsynch protocol in lactating dairy cows". Journal of Dairy Science, 90(10), 4623-4634.00220302https://doi.org/10.3168/jds.2007-0172https://www.sciencedirect.com/science/article/pii/S0022030207719264http://hdl.handle.net/11452/28168The aim of this study was to determine whether an increase in circulating estrogen concentrations would increase percentage pregnant per artificial insemination (PP/AI) in a timed AI protocol in high-producing lactating dairy cows. We analyzed only cows having a synchronized ovulation to the last GnRH of the Ovsynch protocol (867/1,084). The control group (n = 420) received Ovsynch (GnRH - 7 d - PGF2α - 56 h - GnRH -16 h - timed AI). The treatment group (n = 447) had the same timed AI protocol with the addition of 1 mg of estradiol-17β (E2) at 8 h before the second GnRH injection. Ovarian ultrasound and blood samples were taken just before E2 treatment of both groups. In a subset of cows (n = 563), pressure-activated estrus detection devices were used to assess expression of estrus at 48 to 72 h after PGF2α treatment. Ovulation was confirmed by ultrasound 7 d after timed AI. Treatment with E2 increased expression of estrus but overall PP/ AI did not differ between E2 and control cows. There was an interaction between treatment and expression of estrus such that PP/AI was greater in E2-treated cows that showed estrus than in E2-treated or control cows that did not show estrus and tended to be greater than control cows that showed estrus. There was evidence for a treatment by ovulatory follicle size interaction on PP/AI. Supplementation with E2 improved PP/ AI in cows ovulating medium (15 to 19 mm) but not smaller or larger follicles. The E2 treatment also tended to improve PP/AI in primiparous cows with low (S2.5) body condition score, and in cows at first postpartum service compared with Ovsynch alone. In conclusion, any improvements in PP/AI because of E2 treatment during a timed AI protocol appear to depend on expres sion of estrus, parity, body condition score, and size of ovulatory follicle.eninfo:eu-repo/semantics/openAccessConception rateDairy cowEstradiolOvsynchBosTimed artificial-inseminatioOvulatory follicleEstrous behaviorReproductive-performanceCirculating steroidsSperm transportBody conditionPregnancy rateDry cowsProgesteroneAbortion, veterinaryAnimalsBody constitutionCattleDairyingParityEstradiolPredictive value of testsEstrogensLactationEstrusFemaleOvarian follicleFertilityGonadotropin-releasing hormoneInsemination, artificialPregnancyPregnancy rateProgesteroneTemperatureArticle0002495837000132-s2.0-3574897234446234634901017881683Agriculture, dairy & animal scienceFood science & technologyArtificial Insemination; Estrus; Estrus SynchronizationGonadorelinEstradiolEstrogenProgesteroneAnimalCattlePregnancyAnimal diseaseArtificial inseminationBloodArticle body constitutionDairyingPrediction and forecastingClinical trialControlled clinical trialControlled studyEstrusDrug effectEchographyFemaleFertilityLactationMethodologyOvary follicleParityPhysiologyPregnancy rateRandomized controlled trialTemperatureVeterinary abortion