Maintenance of pregnancy in postpartum beef cows that have short-lived corpora lutea.
The first two experiments examined the role of the uterus in low pregnancy rates of beef cows induced to ovulate by early weaning. At 20 to 25 d postpartum, one-half of the cows in Exp. 1 and 2 received a s.c. implant containing 6 mg of norgestomet (NOR) for 9 d (NOR-pretreated) and the remaining cows were untreated controls (CON). Lengths of first postpartum luteal phase after weaning of calves at d 7 after implant insertion were expected to be normal in NOR-pretreated and short in CON cows. In Exp. 1, cows of both groups received an implant containing 3 mg of NOR at d 4 after first estrus and a silastic implant with 15 or 25 mg of NOR at d 7 after first estrus. At 7 d after first estrus, two embryos were transferred into the uterus of each cow and pregnancy was diagnosed by ultrasonography at d 35. Blood samples were collected daily from onset of treatment to d 8 after estrus and then every other day to d 24. Only 4 of 22 cows were pregnant at d 35, concentrations of estradiol (E2) were elevated after luteolysis, and large follicles were present at d 35. In Exp. 2, all cows were injected with 100 mg of progesterone (P4) twice daily from d 4 to 35 after first estrus. Embryos were transferred, pregnancy was diagnosed, and blood samples were collected as in Exp. 1, except blood sampling was continued to d 34.(ABSTRACT TRUNCATED AT 250 WORDS)
Butcher
R L
RL
West Virginia University, Morgantown 26506-9186.
Reber
J E
JE
Lishman
A W
AW
Breuel
K F
KF
Schrick
F N
FN
Spitzer
J C
JC
Inskeep
E K
EK
D000818:Animals; D002417:Cattle / Q000502:physiology*; D004343:Drug Implants; D004624:Embryo Transfer / Q000662:veterinary; D004958:Estradiol / Q000097:blood; D005260:Female; D008183:Luteal Phase / Q000187:drug effects* / Q000502:physiology; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000502:physiology; D049590:Postpartum Period / Q000187:drug effects* / Q000502:physiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D011270:Pregnancy, Animal / Q000187:drug effects* / Q000502:physiology; D011282:Pregnenediones / Q000008:administration & dosage / Q000494:pharmacology*; D011374:Progesterone / Q000097:blood; D045167:Progesterone Congeners / Q000008:administration & dosage / Q000494:pharmacology; D011897:Random Allocation; D014463:Ultrasonography; D014599:Uterus / Q000502:physiology
D004343:Drug Implants; D011282:Pregnenediones; D045167:Progesterone Congeners; C100284:norgestomet; D011374:Progesterone; D004958:Estradiol