title: Short communication: Plasma progesterone concentration and ovarian dynamics of lactating Jersey cows treated with 1 or 2 intravaginal progesterone inserts.
abstract: The objectives of the current experiment were to determine circulating progesterone concentrations and ovarian follicle development of lactating Jersey cows treated with 1 or 2 controlled internal drug release (CIDR) insert containing 1.38 g of progesterone during proestrus. Cows were enrolled in the experiment at 34 ± 3 d in milk and were paired by parity, body condition score, body weight, and milk yield. Estrous cycles were presynchronized with an injection of GnRH concurrent with a new CIDR insert (study d -7) and 2 injections of PGF2α given 5 and 6 d after the GnRH injection (study d -2 and -1, respectively). Cows assigned to the 1CIDR treatment (n=30) or 2CIDR treatment (n=30) received 1 and 2 CIDR inserts, respectively, from study d 0 through 7. Control cows (n=10) did not receive further treatment. On study d -2 and daily from study d 0 through 7, ovaries were examined by transrectal ultrasound and blood samples were collected for determination of progesterone. On study d 7, CIDR inserts were removed after ultrasound exam and blood sample collection. Progesterone concentration from study d 0 through 7 was greatest for 2CIDR cows (2.17 ± 0.09 ng/mL), followed by 1CIDR cows (1.37 ± 0.10 ng/mL) and control cows (0.62 ± 0.21 ng/mL). The interaction between treatment and study day affected progesterone concentration from study d 0 through 7. The average increase in progesterone concentration from study d 1 through 7 was 0.80 ng/mL for 1CIDR and 1.72 ng/mL for 2CIDR cows compared with control cows. The percentage of cows that ovulated between study d 0 and 7 was greatest for control cows (80%), but it did not differ between 1CIDR (12%) and 2CIDR (3.7%) cows. Growth of class III follicles (10-17 mm) identified on study d 0 was affected by treatment because 1CIDR cows had larger class III follicles than 2CIDR cows on study d 5, 6 and 7. A larger proportion of control cows developed a new follicular wave between study d 0 and 7 (control=60.0%, 1CIDR=12.0%, 2CIDR=7.4%). Treatment of lactating Jersey cows with 1 and 2 CIDR inserts resulted in a 1 and 2 fold increase, respectively, in circulating progesterone concentration. Growth class III follicles from cows treated with 2 CIDR inserts was reduced compared with untreated cows and cows treated with 1 CIDR insert.
authors.affiliation: Department of Veterinary Population Medicine, University of Minnesota, Saint Paul 55108.
authors.forename: João G N
authors.initials: JGN
authors.lastname: Moraes
authors.affiliation: Department of Veterinary Population Medicine, University of Minnesota, Saint Paul 55108.
authors.forename: Paula R B
authors.initials: PRB
authors.lastname: Silva
authors.affiliation: Department of Large Animal Clinical Sciences, University of Florida, Gainesville 32608.
authors.forename: Nathália
authors.initials: N
authors.lastname: Bortoletto
authors.affiliation: Department of Large Animal Clinical Sciences, University of Florida, Gainesville 32608.
authors.forename: Alexandre L A
authors.initials: ALA
authors.lastname: Scanavez
authors.affiliation: Department of Large Animal Clinical Sciences, University of Florida, Gainesville 32608; Department of Animal Sciences, University of Florida, Gainesville 32608. Electronic address: rcchebel@ufl.edu.
authors.forename: Ricardo C
authors.initials: RC
authors.lastname: Chebel
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations / Q000378:metabolism; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation; D006080:Ovarian Follicle / Q000254:growth & development*; D011374:Progesterone / Q000097:blood*
chemical_list: D003692:Delayed-Action Preparations; D011374:Progesterone
keywords: follicle development; intravaginal progesterone insert; lactating Jersey cow; plasma concentration