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Effects of supplemental progesterone using a CIDR insert on pregnancy per embryo transfer of dairy heifer recipients of embryos produced in vitro
- Steichen, Melissa M., Larson, Jamie E.
- Animal reproduction science 2019
- Holstein, blood sampling, blood serum, controlled internal drug release devices, embryo transfer, freeze-thaw cycles, heifers, pregnancy, progesterone, ultrasonography
- The objective of this experiment was to evaluate effects of supplemental progesterone immediately following transfer of frozen-thawed, IVP embryos on P/ET. Holstein heifers (n = 452), allocated to nine transfer groups over time, were assigned to be embryo recipients in a completely randomized study from December 2016 to April 2017. All heifers were randomly assigned to one of two treatments: 1) control (CON; n = 212) with no further treatment, or 2) received a CIDR insert containing progesterone for 12 d, beginning on the day of transfer (D 7) and removed 12 d later on Day 19 (CIDR; n = 228). A subset of heifers were subjected to blood sampling on Day 7 (ET) and Day 19 (CIDR removal) to determine circulating concentrations of progesterone. Pregnancy was initially determined using a serum assay for pregnancy specific protein-B at approximately Day 40 after ET and confirmed a month later using trans-rectal ultrasonography. Overall, P/ET did not differ (P = 0.941) between treatment groups. At the initial pregnancy determination, P/ET differed (P = 0.007) among transfer groups. Concentrations of progesterone tended to be less (P = 0.064) in heifers in the CON group compared to heifers treated with the CIDR (3.6 ± 0.27 compared with 4.4 ± 0.27 ng/mL), and differed between transfer groups (P < 0.001) and days post-estrus (P = 0.019) of the recipients. In summary, while treatment with supplemental progesterone at the time of transfer of IVP embryos using a CIDR increased circulating progesterone, there was no influence on P/ET.