title: Elevated progesterone concentrations enhance prostaglandin F2alpha synthesis in dairy cows.
abstract: The objective was to evaluate the influence of varying plasma progesterone (P(4)) concentrations throughout the luteal phase in dairy cows on PGF(2alpha) production (assessed as plasma concentrations of 13,14-dihydro-15-keto-PGF(2alpha); PGFM) following treatment with estradiol-17beta (E(2)) or oxytocin (OT). In all experiments, time of ovulations was synchronized with the OvSynch protocol and Day 0 corresponded to day of second GnRH injection. In Experiment 1, non-lactating dairy cows on Day 6 remained non-treated (n=9), received 20mg LH (n=7), or had ovarian follicles larger than 6mm aspirated (n=8). In Experiment 2, cows on Day 6 were untreated (n=9) or received 5000 IU hCG (n=10). In Experiments 1 and 2, all cows received 3mg E(2) on Day 17, and blood samples were collected every 30 min from 2h before to 10h after E(2). Experiment 3 was conducted in two periods, each from Days 0 to 17 of the estrous cycle. At the end of Period 1, animals switched treatments in a crossover arrangement. Animals in Group 2/8 (n=4) received 2 kg/d of concentrate in the first period and 8 kg/d in the second period. Animals in Group 8/2 (n=7) received the alternate sequence. Blood was collected daily for measurement of P(4) 4h after concentrate feeding. On Day 17, blood was collected from 1h before to 1h after a 100 IU OT injection. In Experiment 1, both plasma P(4) and release of PGF(2alpha) were similar between LH-treated and control cows (P>0.10). In Experiment 2, plasma P(4) was elevated to a greater extent on Day 17 in cows treated with hCG (P<0.05) and plasma PGFM was also greater in hCG-treated animals (treatment x time interaction; P<0.05). In Experiment 3, there was a group x period interaction (P<0.01) for plasma P(4), indicating that less concentrate feeding was associated with greater plasma P(4). Release of PGF(2alpha) in response to OT was greater for cows receiving less concentrate (group x period interaction; P<0.05). In conclusion, dairy cows with more elevated blood P(4) concentrations released more PGF(2alpha) in response to E(2) or OT.
authors.affiliation: Escola Agrotécnica Federal, Uberlândia, MG, Brazil.
authors.forename: Ricarda Maria
authors.initials: RM
authors.lastname: dos Santos
authors.forename: Marcelo Demarchi
authors.initials: MD
authors.lastname: Goissis
authors.forename: David Augusto
authors.initials: DA
authors.lastname: Fantini
authors.forename: Claudia Maria
authors.initials: CM
authors.lastname: Bertan
authors.forename: José Luiz Moraes
authors.initials: JL
authors.lastname: Vasconcelos
authors.forename: Mario
authors.initials: M
authors.lastname: Binelli
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood*; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D015237:Dinoprost / Q000096:biosynthesis* / Q000097:blood*; D004958:Estradiol / Q000494:pharmacology; D030762:Estrous Cycle; D005260:Female; D005300:Fertility Agents, Female / Q000494:pharmacology; D010121:Oxytocin / Q000494:pharmacology; D011374:Progesterone / Q000097:blood*; D013997:Time Factors
chemical_list: D006063:Chorionic Gonadotropin; D005300:Fertility Agents, Female; D011374:Progesterone; D004958:Estradiol; D010121:Oxytocin; D015237:Dinoprost