Pregnancy outcomes after change in dose delivery of prostaglandin F₂α and time of gonadotropin-releasing hormone injection in a 5-day timed artificial insemination program in lactating dairy cows

We demonstrated that 50mg of PGF₂α on d 6 successfully induced luteolysis in lactating dairy cows enrolled in a traditional 5-d Ovsynch-72 program [GnRH injection 5 d before (d 0; GnRH-1) and 56 (p.m. on d 7; GnRH-2) or 72 h (d 8; GnRH-2) after a 25-mg injection of PGF₂α (d 5 and 6 after GnRH inject...

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Bibliographic Details
Published in:Journal of dairy science 2014-12, Vol.97 (12), p.7586-7594
Main Authors: Stevenson, J S, Pulley, S L, Hill, S L
Format: Article
Language:English
Subjects:
Animals
Cattle - physiology
Corpus Luteum - drug effects
Delivery, Obstetric - veterinary
Dinoprost - administration & dosage
Estrus Synchronization
Female
Gonadotropin-Releasing Hormone - administration & dosage
Insemination, Artificial - veterinary
Lactation - drug effects
Lactation - physiology
Luteolysis - drug effects
Pregnancy
Pregnancy Outcome
Progesterone - blood
Time Factors
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Summary:We demonstrated that 50mg of PGF₂α on d 6 successfully induced luteolysis in lactating dairy cows enrolled in a traditional 5-d Ovsynch-72 program [GnRH injection 5 d before (d 0; GnRH-1) and 56 (p.m. on d 7; GnRH-2) or 72 h (d 8; GnRH-2) after a 25-mg injection of PGF₂α (d 5 and 6 after GnRH injection); timed artificial insemination (AI) on d 8]. Our current objective was to determine pregnancy outcomes in lactating dairy cows after a 50-mg injection of PGF₂α on d 6 or a 25-mg injection of PGF₂α on d 5 and 6 in a 5-d Ovsynch program. Cows in herd 1 diagnosed not pregnant between 30 and 36 d since last AI were enrolled to receive either a 50-mg injection of PGF₂α on d 6 (1 × 50; n=134) or a 25-mg injection of PGF₂α on d 5 and 6 (2 × 25; n=139) after GnRH-1 (d 0), with GnRH-2 at 72 h after PGF₂α injection (d 5), concurrent with timed AI (d 8). Cows in herd 2 diagnosed not pregnant between 34 and 40 d were treated similarly: even-tagged cows received the 2 × 25 (n=422) treatment, and odd-tagged cows received the 1 × 50 (n=450) treatment, except that GnRH-2 was administered at 56 h. Blood collected from cows in herd 1 at d 0, 5, 6, and 8 was assayed for progesterone. Luteolysis was defined to occur when progesterone concentration was ≥1 ng/mL on d 5, and 72 h later (d 8) was either
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.2014-8312