Abstract
We appreciate the donations of CIDR inserts and Lutalyse (Pfizer Animal Health, New York, NY), Pregnecol 6000 and Norvomon 5000 (John Hasler, Bioniche, Canada), and Fertagyl and Estrumate (Intervet-Schering Plough Animal Health, Millsboro, DE to conduct this study. Partial funding was provided by Select Sires Inc., Plain City, OH.
Highlights
Cows inseminated at first service after detected estrus have better conception rates than those inseminated by appointment in an ovulation-synchronization program (40.7 vs. 33.5%; Stevenson and Phatak, Dairy Research 2009, Report of Progress 1021, pp. 56-62), but not as good as cows in estrus at the timed artificial insemination (AI; 51.8%)
The objective of this study was to evaluate the effects of equine chorionic gonadotropin on various characteristics associated with an effective timed artificial insemination (AI) protocol in lactating dairy cows
Cows (n = 121) in a single herd were treated with 2 injections of prostaglandin F2α (PGF2α) 14 days apart (Presynch), with the second injection administered 11 days before the onset of a timed AI protocol
Summary
Cows inseminated at first service after detected estrus have better conception rates than those inseminated by appointment in an ovulation-synchronization program (40.7 vs. 33.5%; Stevenson and Phatak, Dairy Research 2009, Report of Progress 1021, pp. 56-62), but not as good as cows in estrus at the timed artificial insemination (AI; 51.8%). Because dairy cows have greater rates of metabolism of steroids and produce large quantities of milk, their circulating concentrations of progesterone and estradiol are less in comparison with nonlactating heifers despite having larger corpora lutea (CL) and larger follicles, respectively. Equine chorionic gonadotropin (eCG) is a member of the glycoprotein family, which includes follicle stimulating hormone (FSH) and luteinizing hormone (LH). It is secreted by the trophoblast cells of the chorionic girdle in the pregnant mare beginning approximately at 37 days of gestation. The FSH properties of eCG have led to its use as an exogenous hormone preparation for stimulation of follicular growth and superovulation in farm animals
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