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

Autor:	Bilby TR; Texas A&M AgriLife Research and Extension, Texas A&M System, Stephenville 76401. Electronic address: todd.bilby@merck.com., Bruno RGS; Texas A&M AgriLife Research and Extension, Texas A&M System, Stephenville 76401., Lager KJ; Texas A&M AgriLife Research and Extension, Texas A&M System, Stephenville 76401., Chebel RC; Department of Veterinary Population Medicine, University of Minnesota, Saint Paul 55108., Moraes JGN; Department of Veterinary Population Medicine, University of Minnesota, Saint Paul 55108., Fricke PM; Department of Dairy Science, University of Wisconsin, Madison 53706., Lopes G Jr; Department of Dairy Science, University of Wisconsin, Madison 53706., Giordano JO; Department of Dairy Science, University of Wisconsin, Madison 53706., Santos JEP; Department of Animal Sciences, University of Florida, Gainesville 32611., Lima FS; Department of Animal Sciences, University of Florida, Gainesville 32611., Stevenson JS; Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506., Pulley SL; Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506.
Jazyk:	angličtina
Zdroj:	Journal of dairy science [J Dairy Sci] 2013; Vol. 96 (11), pp. 7032-7042. Date of Electronic Publication: 2013 Sep 05.
DOI:	10.3168/jds.2013-6960
Abstrakt:	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 ± 3 d post-AI to 1 of 4 resynchronization (RES) treatments arranged in a 2 × 2 factorial design using the Ovsynch-56 (GnRH, 7d later PGF2α, 56 h later GnRH, 16 h later TAI) protocol. Treatments were as follows: cows initiating RES 32 ± 3 d 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 ± 3 d 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 60 d 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 PGF2α 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 PGF2α was greater for d 32 than for d 39 cows (87.9 vs. 79.4%). In addition, percentage of cows with P4 ≥ 1 ng/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 PGF2α of the RES protocols (86.5 vs. 74.3%). Treatment did not affect ovulation to G1 or P/AI 32 d 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 60 d 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 60 d 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 <1 ng/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 ≥ 1 ng/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 ± 3 d after AI but not 32 ± 3 d after AI. (Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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