title: Estradiol benzoate given 0 or 24 h after the end of a progestagen treatment in postpartum suckled beef cows.
abstract: The objective of Experiment 1 was to compare the effects of estradiol benzoate (EB) given 0 or 24h after the end of a progestagen treatment on ovulation and CL formation in anestrous cows. Twenty cows were treated with an intravaginal sponge containing 250 mg of medroxiprogesterone acetate (MPA). At sponge insertion, each cow received 3 mg EB and 10 mg MPA im. At device removal, cows received 0.7 mg EB either at that time (EB0) or 24h later (EB24). Ultrasound examinations and blood sampling to determine plasma progesterone concentrations were performed to detect ovulation and CL formation. Ovulation occurred in 77.8 and 81.8% cows in the EB0 and EB24 groups, respectively. Diameter of the ovulatory follicle (EB0 = 10.9 +/- 0.5mm; EB24 = 12.1 +/- 0.8 mm; P = 0.26) and the interval from sponge removal to ovulation (median = 3 days; P = 0.64) did not differ between treatments. Among the cows that ovulated (n = 16), short-lived CL were present in 2/7 and 2/9 cows in the EB0 and EB24 groups, respectively. Plasma progesterone concentrations and CL area did not differ between treatments (P > 0.05). In Experiment 2, cows were treated with the same protocol as in Experiment 1, but at sponge withdrawal all cows received 250 microg cloprostenol and timed artificial insemination (TAI) was performed 48 h after sponge removal. In Replicate 1 (n = 204 multiparous cows), pregnancy rates were 45.0 and 47.5% for EB0 and EB24, respectively (P > 0.05). In Replicate 2 (n = 69 primiparous cows) pregnancy rate did not differ between EB0 and EB24 (51.4% versus 52.9%). In conclusion, EB given 0 or 24h after the end of a progestagen treatment had the same effect on ovulation rate, time to ovulation, diameter of the ovulatory follicle, incidence of short-lived CL, luteal tissue area, and plasma progesterone concentrations of normal lifespan CL, and pregnancy rate after TAI in suckled beef cows.
authors.affiliation: Escuela de Posgrado en Producción Animal, Facultad de Ciencias Agrarias, Universidad Nacional de Mar del Plata, C.C. 276 Balcarce 7620, Argentina. rosspabl@msu.edu
authors.forename: Pablo Juan
authors.initials: PJ
authors.lastname: Ross
authors.forename: Juan Florencio
authors.initials: JF
authors.lastname: Aller
authors.forename: Santiago Saul
authors.initials: SS
authors.lastname: Callejas
authors.forename: Horacio
authors.initials: H
authors.lastname: Butler
authors.forename: Ricardo Horacio
authors.initials: RH
authors.lastname: Alberio
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003008:Cloprostenol / Q000008:administration & dosage; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology; D004958:Estradiol / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D004973:Estrus Synchronization; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary; D007700:Kinetics; D007774:Lactation; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage*; D010053:Ovary / Q000000981:diagnostic imaging; D010060:Ovulation / Q000187:drug effects*; D049590:Postpartum Period; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D013997:Time Factors; D014463:Ultrasonography
chemical_list: C074283:estradiol 3-benzoate; D003008:Cloprostenol; D011374:Progesterone; D004958:Estradiol; D017258:Medroxyprogesterone Acetate