Effect of age and norgestomet on endocrine parameters and production of embryos in superovulated beef cows.
Effects of age of cow and a norgestomet (N) implant on number of embryos and endocrine responses to induction of superovulation were studied in old (greater than 12 yr) and young (5 to 7 yr) lactating beef cows. Seventeen cows (8 old and 9 young) received a 6-mg N ear implant on d 4 or 5 of the cycle (d 0 = estrus); the remaining 17 cows (9 old and 8 young) served as untreated controls (C). All animals were treated with 38 mg of porcine follicle-stimulating hormone (FSH-P) in decreasing dosages over a 4.5-d period beginning on d 10 or 11. Regression of the corpus luteum was induced with injections of PGF2 alpha at 0800 and 2000 on d 4 of FSH-P treatment; implants were removed at the second injection of PGF2 alpha. Cows were inseminated artificially 12 and 24 h after onset of estrus. Embryos were collected on d 7 or 8 postinsemination. Blood samples were obtained daily at 0800 from 2 d prior to initiation of treatment with FSH-P until collection of embryos. An additional sample was collected each day at 2000, from the first injection of PGF2 alpha to 1 d after onset of estrus. Samples were assayed for luteinizing hormone (LH), progesterone (P4), follicle stimulating hormone (FSH) and estradiol-17 beta (E2). Total number of embryos plus ova recovered was lower (P less than .01) in N-treated (5.2 +/- 1.1) than in C-treated (10.6 +/- 1.6) cows.(ABSTRACT TRUNCATED AT 250 WORDS)
Garcia-Winder
M
M
West Virginia University, Morgantown 26506-6302.
Lewis
P E
PE
Bryner
R W
RW
Baker
R D
RD
Inskeep
E K
EK
Butcher
R L
RL
D000367:Age Factors; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004343:Drug Implants; D004622:Embryo, Mammalian / Q000187:drug effects*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D010060:Ovulation / Q000187:drug effects*; D011247:Pregnancy; D011282:Pregnenediones / Q000008:administration & dosage / Q000494:pharmacology*; D045167:Progesterone Congeners / Q000008:administration & dosage / Q000494:pharmacology*; D013480:Superovulation / Q000187:drug effects*
D004343:Drug Implants; D011282:Pregnenediones; D045167:Progesterone Congeners; C100284:norgestomet; D005640:Follicle Stimulating Hormone