Ovulation in postpartum beef cows treated with estradiol.

摘要: The effect of implants estradiol on initiation ovarian cycles postpartum was studied in 201 anestrous beef cows. Cows from four farms were used over a 2-yr period 2 x 3 factorial arrangement treatments with and stage as main effects. assigned at random within date calving farm to receive an ear implant containing estradiol-17 beta (24 mg) for 21 d or serve controls. Stages implantation divided into less than equal 25, 26 39, greater 40 d, three stages that should reflect potential changes hypothalmic-hypophysial sensitivity estradiol. Blood samples determination progesterone obtained rectal examinations the ovaries performed insertion, 14 after removal (d 21), 35) assess ovulatory response treatment. Circulating concentrations treatment averaged 3.2 +/- 1.0 23.1 4.7 pg/ml control estradiol-treated cows, respectively. Compared initiated increased proportion cows ovulated during experimental period. No differences seen average days when first determined have ovulated.