Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10973798 | Journal of Dairy Science | 2015 | 7 Pages |
Abstract
The luteal structure that develops postovulation is critical to the facilitation and maintenance of pregnancy in dairy cattle. The objectives of this experiment were to determine if the induction of an accessory corpus luteum (CL), via human chorionic gonadotropin, altered blood perfusion of CL, peripheral concentrations of progesterone, or hepatic steroid-inactivating enzymes. Twenty-eight late-lactation Holstein cows were synchronized using the Ovsynch protocol and randomly assigned to 1 of 2 treatment groups. Cows received either an injection of human chorionic gonadotropin (1,000Â IU, i.m.) to induce an accessory CL (cows had exactly 2Â CL in 1 ovary) or no treatment (cows had exactly 1Â CL). Corpora lutea were examined daily from d 10 to 18 (d 0 was induced ovulation) via Doppler ultrasonography and a blood sample was collected. Volume of the CL was recorded, as well as images and videos of each CL, which were analyzed for blood perfusion. On d 13, a liver biopsy was performed to analyze hepatic steroid-inactivating enzymes. Cows with 1 or 2Â CL had similar peripheral concentrations of progesterone. Cows with 2Â CL had similar luteal volumes to cows with 1Â CL but cows with 2Â CL had greater total luteal blood perfusion. Hepatic enzyme [cytochrome P450 (CYP) 1A, 3A, and 2C, aldo-keto reductase 1C, and uridine diphosphate glucuronosyltransferase] activities did not differ between cows with 1 and 2Â CL. Overall, the observed increase in total luteal blood perfusion in cows with 2Â CL did not correspond to differences in peripheral concentrations of progesterone or clearance of progesterone measured by the hepatic enzyme activity. This could indicate that induction of an accessory CL would not affect concentrations of progesterone necessary to maintain pregnancy.
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Authors
B.E. Voelz, G.F. Cline, C.G. Hart, C.O. Lemley, J.E. Larson,