title: Genetic merit for fertility traits in Holstein cows: V. Factors affecting circulating progesterone concentrations.
abstract: This study investigated the factors affecting circulating progesterone (P4) concentrations in cows with similar genetic merit for milk production traits, but with extremes of good (Fert+) or poor (Fert-) genetic merit for fertility traits. Study 1: 28 cows were enrolled in an ovulation synchronization protocol at 61±13 (±standard deviation) days postpartum, and data are presented for 13 Fert+ and 9 Fert- cows that remained in the study. Progesterone concentrations were determined from d 0 to 9 (d 0=estrus) and on d 7, corpus luteum (CL) volume and blood flow area (BFA) were measured by B-mode and Doppler ultrasonography, respectively. Cows were administered PGF2α on d 7 in the p.m. and d 8 in the a.m. to regress the CL, and 2 controlled internal drug release devices were inserted per vaginum on d 8 in the a.m. Liver biopsies were collected on d 9 and hepatic mRNA abundance of genes involved in P4 catabolism was determined. On d 10, the controlled internal drug release inserts were removed and frequent blood samples were collected to measure the rate of decline in circulating P4. The Fert+ cows tended to have greater dry matter intake compared with Fert- cows (+0.79kg of dry matter/d), but similar milk production (29.82kg/d). After synchronized ovulation, the rate of increase in circulating P4 concentrations was greater in Fert+ cows compared with Fert- cows. No effect of genotype on CL volume was detected, but BFA was 42% greater in Fert+ cows compared with Fert- cows. The Fert- cows had greater mRNA abundance of cytochrome P450, family 3, subfamily A (CYP3A) compared with Fert+ cows, but the mRNA abundance of aldo-keto reductase family 1, member C1 (AKR1C1), AKR1C3, AKR1C4, and cytochrome P450, family 2, subfamily C (CYP2C) were similar. The half-life and metabolic clearance rate of P4 were similar in Fert+ cows and Fert- cows. Study 2: 23 cows were enrolled in an ovulation synchronization protocol at 55±7 (±standard deviation) d postpartum, and data are presented for 13 Fert+ and 8 Fert- cows that remained in the study. On d 4, 7, 10, and 13 (d 0=estrus), CL volume and BFA were measured as in study 1. Progesterone concentrations were measured from d 1 to 13. Corpus luteum volume was 41% greater in Fert+ cows compared with Fert- cows but no effect of genotype on BFA was detected. Mean circulating P4 concentrations were 79% greater in Fert+ cows compared with Fert- cows. Milk yield was similar in both genotypes. The results indicate that greater circulating P4 concentrations were primarily due to greater CL P4 synthetic capacity rather than differences in P4 clearance in this lactating cow genetic model of fertility.
authors: Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland; School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: S G
authors: SG
authors: Moore
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: S
authors: S
authors: Scully
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: J A
authors: JA
authors: Browne
authors: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors: T
authors: T
authors: Fair
authors: Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland. Electronic address: stephen.butler@teagasc.ie.
authors: S T
authors: ST
authors: Butler
mesh_terms: D015089:20-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002417:Cattle / Q000235:genetics*; D003338:Corpus Luteum / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D015237:Dinoprost / Q000008:administration & dosage; D004958:Estradiol / Q000097:blood; D004971:Estrus / Q000097:blood; D004973:Estrus Synchronization; D005260:Female; D005298:Fertility / Q000235:genetics*; D005838:Genotype; D007774:Lactation / Q000502:physiology; D008892:Milk / Q000378:metabolism; D023421:Models, Animal; D010641:Phenotype; D011374:Progesterone / Q000097:blood*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; C400322:cytochrome P-450 CYP2C subfamily; D011374:Progesterone; D004958:Estradiol; D003577:Cytochrome P-450 Enzyme System; D015237:Dinoprost; D015089:20-Hydroxysteroid Dehydrogenases; D051544:Cytochrome P-450 CYP3A
keywords: corpus luteum; genetic merit for fertility; progesterone; progesterone metabolism