Supplemental progesterone and timing of resynchronization on pregnancy outcomes in lactating dairy cows

T. R. Bilby, R. G.S. Bruno, K. J. Lager, R. C. Chebel, J. G.N. Moraes, P. M. Fricke, G. Lopes, J. O. Giordano, J. E.P. Santos, F. S. Lima, J. S. Stevenson, S. L. Pulley

Research output: Contribution to journalArticlepeer-review


The objective was to determine the effect of exogenous progesterone (P4) in a timed artificial insemination (TAI) protocol initiated at 2 different times post-AI on pregnancies per AI (P/AI) in lactating dairy cows. Cows (n=1,982) in 5 dairy herds were assigned randomly at a nonpregnancy diagnosis 32±3d post-AI to 1 of 4 resynchronization (RES) treatments arranged in a 2×2 factorial design using the Ovsynch-56 (GnRH, 7d later PGF, 56h later GnRH, 16h later TAI) protocol. Treatments were as follows: cows initiating RES 32±3d after AI with no supplemental P4 (d 32 RES-CON; n=516); same as d 32 RES-CON plus a controlled internal drug release (CIDR) insert containing P4 at the onset of Ovsynch-56 (d 32 RES-CIDR; n=503); cows initiating RES 39±3d after AI (d 39 RES-CON; n=494); and same as d 39 RES-CON plus a CIDR (d 39 RES-CIDR; n=491). Cows were inseminated if observed in estrus before TAI. The P/AI was determined 32 and 60d after TAI. In a subgroup of cows (n=1,152), blood samples were collected and ovarian structures examined by ultrasonography on the days of the first GnRH (G1) and PGF of Ovsynch-56. Percentage of cows with a corpus luteum (CL) at G1 was unaffected by timing of treatments, but percentage of cows with a CL at PGF was greater for d 32 than for d 39 cows (87.9 vs. 79.4%). In addition, percentage of cows with P4 ≥1ng/mL at G1 was unaffected by timing of treatments, but was increased for d 32 compared with d 39 RES cows on the day of the PGF of the RES protocols (86.5 vs. 74.3%). Treatment did not affect ovulation to G1 or P/AI 32d after RES TAI (d 32 RES-CON=30.1%, d 32 RES-CIDR=28.8%, d 39 RES-CON=27.5%, d 39 RES-CIDR=30.5%). A greater percentage of d 39 RES cows underwent premature luteolysis during the RES protocol compared with d 32 RES cows. An interaction was detected between day of RES initiation and CIDR treatment, in which the CIDR increased P/AI 60d after TAI for d 39 (CON=23.7% vs. CIDR=28.0%), but not for d 32 (CON=26.9% and CIDR=24.2%) cows. Pregnancy loss was unaffected by treatment. In addition, cows had improved P/AI 60d after TAI when they received a CIDR and did not have a CL (CON-CL=28.2%, CON-No CL=19.2%, CIDR-CL=27.0%, and CIDR-No CL=26.5%) or had P4 <1ng/mL (CON-High P4=27.8%, CON-Low P4=15.0%, CIDR-High P4=25.0%, and CIDR-Low P4=29.4%) at G1, but not if a CL was present or P4 was ≥1ng/mL at G1. In conclusion, addition of a CIDR insert to supplement P4 during the RES protocol increased P/AI for cows initiating RES 39±3d after AI but not 32±3d after AI.

Original languageEnglish (US)
Pages (from-to)7032-7042
Number of pages11
JournalJournal of Dairy Science
Issue number11
StatePublished - Nov 2013


  • Controlled internal drug release insert
  • Dairy cow
  • Resynchronization

ASJC Scopus subject areas

  • Food Science
  • Animal Science and Zoology
  • Genetics

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