The variability in the interval between estrus and ovulation in cattle and its determinants

摘要: Abstract Fertility of Holstein cows has been decreasing for years and, to a lesser extent, the fertility heifers too but more recently. A hypothesis explain this phenomenon may be that chronology events leading ovulation is different those animals bred nowadays when compared what was reported previously; would result in an inappropriate time insemination. Therefore, two experiments were designed investigate relationships among estrus behavior, follicular growth, hormonal and heifers. In first experiment, onset estrus, patterns estradiol-17β, progesterone LH, studied 12 cyclic had their synchronized using Crestar method; done twice, 3 weeks apart. The intervals between ovulation, LH peak, peak were, respectively, 38.5 h ±3.0 , 9.1±2.0 29.4 ±1.5 (mean±S.E.M.). variation interval explained 80.6% ovulation. correlated with estradiol-17β value (r=−0.423, P