title: Efficacy of timed embryo transfer with fresh and frozen in vitro produced embryos to increase pregnancy rates in heat-stressed dairy cattle.
abstract: Our objective was to determine whether pregnancy rates in heat-stressed dairy cattle could be enhanced by timed embryo transfer of fresh (nonfrozen) or frozen-thawed in vitro-derived embryos compared to timed insemination. Ovulation in Holstein cows was synchronized by a GnRH injection followed 7 d later by PGF2 alpha and a second treatment with GnRH 48 h later. Control cows (n = 129) were inseminated 16 h (d 0) after the second GnRH injection. On d 7, a fresh (n = 133) or frozen-thawed (n = 142) in vitro-derived embryo was transferred to cows assigned for timed embryo transfer after categorizing the corpus luteum by palpation per rectum as 3 (excellent), 2 (good or fair), 1 (poor), and 0 (nonpalpable). Response to the synchronization treatment, determined by plasma progesterone concentration (ng/ml) < or = 1.5 on d 0 and > or = 2.0 on d 7, was 76.2%. Mean plasma progesterone concentration on d 7 increased as the quality of corpus luteum improved from category 0 to 3. Concentrations of progesterone in plasma were elevated (> or = 2.0 ng/ml) at 21 d in 64.7 (fresh embryo), 40.3 (frozen embryo), and 41.4 +/- 0.1% (timed insemination) of cows, respectively. Cows that received a fresh embryo had a greater pregnancy rate at 45 to 52 d than did cows that received a frozen-thawed embryo or timed insemination (14.3 > 4.8, 4.9 +/- 2.3%). Body condition (d 0) of cows influenced the pregnancy rate and plasma progesterone concentrations. In summary, timed embryo transfer with fresh in vitro-produced embryos in heat-stressed dairy cattle improved pregnancy rate relative to timed insemination.
authors.affiliation: Department of Dairy and Poultry Sciences, University of Florida, Gainesville 32611, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Ambrose
authors.forename: M
authors.initials: M
authors.lastname: Drost
authors.forename: R L
authors.initials: RL
authors.lastname: Monson
authors.forename: J J
authors.initials: JJ
authors.lastname: Rutledge
authors.forename: M L
authors.initials: ML
authors.lastname: Leibfried-Rutledge
authors.forename: M J
authors.initials: MJ
authors.lastname: Thatcher
authors.forename: T
authors.initials: T
authors.lastname: Kassa
authors.forename: M
authors.initials: M
authors.lastname: Binelli
authors.forename: P J
authors.initials: PJ
authors.lastname: Hansen
authors.forename: P J
authors.initials: PJ
authors.lastname: Chenoweth
authors.forename: W W
authors.initials: WW
authors.lastname: Thatcher
mesh_terms: D000818:Animals; D001823:Body Composition; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000502:physiology; D015925:Cryopreservation; D004624:Embryo Transfer; D005260:Female; D006358:Hot Temperature; D007315:Insemination, Artificial / Q000662:veterinary; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D013312:Stress, Physiological; D013997:Time Factors
chemical_list: D011374:Progesterone