Introduction of bulls at different days postpartum on resumption of ovarian cycling activity in primiparous beef cows.

摘要: The objective of this study was to evaluate postpartum resumption ovulatory cycles among primiparous, suckled beef cows that were exposed continuously mature bulls beginning at various intervals after calving. We sought determine whether cumulative distributions proportions resuming ovarian and interval from the start bull exposure cycling activity differed (BE) or not (NE) on d 15, 35, 55 Angus x Hereford (n = 56) assigned randomly one six treatments in a 2 (exposure type) 3 (day postpartum) factorial arrangement. Blood samples collected each cow starting -1, every third day until end experiment. An increase baseline progesterone concentrations exceeded 1.0 ng/mL three consecutive used as evidence activity. More (P < 0.05) BE resumed by experiment than NE cows. Proportions did differ 0.30) postpartum. greater for 10-d those during first 40 exposure. 30 either 15 35. Interval calving decreased presence bulls. Day affect 0.21) activity; however, linearly increased. conclude exposing primiparous anovulatory increased proportion exhibit activity, independent Furthermore, progressively later seemed respond more rapidly biostimulatory effect when they earlier anestrous period.