Ovarian response and hormone levels in Holstein cows in different reproductive status treated with Ovsynch and two formulations of progesterone

Abstract

To evaluate the effects of injectable progesterone (P4) in oily suspension, three experiments were carried out in multiparous Holstein cows in different reproductive status: 1) 24 multiparous cows with more than 140 days postpartum (DPP) in anestrus, in three groups: Ovsynch + CIDR, Ovsynch + 200 and Ovsynch + 400 mg of MAD-4. 2) 8 cows in anestrus with less than 100 DPP in two groups: Ovsynch + CIDR and Ovsynch + 200 mg of MAD-4 and 3) 15 repeatbreeder cows cycling with more than 200 DPP in two groups: Ovsynch + 200 and Ovsynch + 400 mg of MAD-4. In all experiments, frequent bleeding and ovarian ultrasonography were carried out. In experiment 1 P4 levels of CIDR Group remained constant at 1.5±0.7 ng/mL. MAD 200 and 400 MAD groups reached P4 levels higher than 10 ng/mL (P<0.05) at 8 h, descending at 48 h to baseline. Diameter of the dominant follicle (DF) at D9 was 5 mm higher in the CIDR that in MAD groups (P<0.05). In experiments 2 and 3 P4 levels were similar to those of experiment 1, as well as the difference in the diameter of the DF at D9. It is concluded that circulating P4 levels after administration of injectable P4 increase excessively at the beginning of the treatment, decreasing rapidly in 48 hours which, in addition to being less effective as a source of P4 in treatments of induction of ovulation that intravaginal, affect the diameter of the induced dominant follicle.