title: Evaluation of the lytic response of prostaglandin F2 alpha in Zebu cattle based on serum progesterone.
abstract: To evaluate by means of blood progesterone levels and estrous expression the effect of the injection of 25 mg of PGF2alpha in Zebu cows, 17 Indobrazil cows with a palpable corpus luteum (CL) were injected with PGF2alpha and blood samples taken every 6 h in Experiment I. In Experiment II, 15 cows from the previous experiment at the same stage of diestrus were injected with PGF2alpha and bled every 4 h for 5 d. Progesterone levels had declined by 50% 6 h after injection in all cows and dropped to below 1 ng/ml by 30 h. Estrus was observed in 47% of the animals in Experiment I and 60% in Experiment II. Ovulation was detected accurately in 29% of the animals at 33.6 +/- 11.6 h after the onset of estrus. The correlation between finding a CL by rectal palpation and levels of progesterone higher than 1 ng/ml of blood was 86 and 93% in Experiments I and II, respectively. These studies indicate that the injection of 25 mg of PGF2alpha is sufficient to produce luteolysis in Zebu cattle, although estrous expression is poor.
authors.affiliation: Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, 04510 México, D.F.
authors.forename: I Y
authors.initials: IY
authors.lastname: Moreno
authors.forename: C S
authors.initials: CS
authors.lastname: Galina
authors.forename: F J
authors.initials: FJ
authors.lastname: Escobar
authors.forename: B
authors.initials: B
authors.lastname: Ramírez
authors.forename: R
authors.initials: R
authors.lastname: Navarro-Fierro