Ability of induced corpora lutea to maintain pregnancy in beef cows.
Experiments were conducted in beef cows without a primary CL, in which pregnancy had been maintained with exogenous progestogen. In preliminary trials, replacement CL induced ipsilateral to the embryo and after, rather than before, d 36 of pregnancy, maintained more pregnancies after withdrawal of exogenous progestogen (13/13 vs 2/6; P < 0.05). In Exp. 1, in cows with replacement CL induced by treatment with hCG on d 28 of pregnancy, treatment with flunixin meglumine on d 31 through 37 did not increase maintenance of pregnancy. Experiment 2 was conducted to evaluate directly the effects of concentrations of PGF2alpha and estradiol-17beta during d 31 through 35 of pregnancy on maintenance of pregnancy by replacement CL induced between d 28 and 31. In cows that maintained pregnancy while progestogen was provided, maintenance of pregnancy after withdrawal of exogenous progestogen tended to be greater with high (5/5) than with low (2/6; P < 0.10) concentrations of PGF2alpha and greater with low (6/7) than with high (2/6; P = 0.10) concentrations of estradiol-17beta. Secretion of progesterone by replacement CL was greater (P < 0.05) in cows with high than in those with low concentrations of PGF2, during d 31 through 35. Prostaglandin F2alpha may facilitate attachment of the bovine embryo (d 30 to 40) in a manner similar to that reported for implantation in other species. Cows that did not form CL in response to hCG on d 28 to 31 responded well when retreated after d 36. Again, maintenance of pregnancy was greater when replacement CL were induced after (9/9) rather than before d 36 (8/16; P < 0.05).
Bridges
P J
PJ
Division of Animal and Veterinary Sciences, West Virginia University, Morgantown 26506, USA.
Wright
D J
DJ
Buford
W I
WI
Ahmad
N
N
Hernandez-Fonseca
H
H
McCormick
M L
ML
Schrick
F N
FN
Dailey
R A
RA
Lewis
P E
PE
Inskeep
E K
EK
D000818:Animals; D002417:Cattle / Q000502:physiology*; D002418:Cattle Diseases / Q000209:etiology; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D003338:Corpus Luteum / Q000502:physiology*; D015237:Dinoprost / Q000097:blood; D005260:Female; D005313:Fetal Death / Q000209:etiology / Q000662:veterinary; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011374:Progesterone / Q000097:blood
D006063:Chorionic Gonadotropin; D011374:Progesterone; D015237:Dinoprost