Progestin-induced puberty and secretion of luteinizing hormone in heifers

Two experiments were designed to investigate the endocrine mechanisms by which progestin administration induces puberty in heifers. In experiment 1, prepubertal heifers were randomly assigned by age to receive either a single norgestomet implant for 10 days (NORG; n = 15) or to serve as unimplanted...

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Bibliographic Details
Published in:Biology of reproduction 1996-05, Vol.54 (5), p.1025-1031
Main Authors: Anderson, L.H. (The Ohio State University, Columbus, OH.), McDowell, C.M, Day, M.L
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Cattle - physiology
Drug Implants
Estradiol - blood
ESTROGENOS
Female
FEMELLE
Fundamental and applied biological sciences. Psychology
GENISSE
HEMBRA
HORMONAS
HORMONAS SINTETICAS
HORMONE
Hormone metabolism and regulation
HORMONE SYNTHETIQUE
Luteinizing Hormone - metabolism
MADUREZ SEXUAL
Mammalian female genital system
MATURITE SEXUELLE
NOVILLA
OESTROGENE
Organ Size
OVAIRE
Ovarian Follicle - diagnostic imaging
Ovarian Follicle - growth & development
OVARIOS
PLASMA SANGUIN
PLASMA SANGUINEO
Pregnenediones - administration & dosage
Pregnenediones - pharmacology
PROGESTAGENE
PROGESTAGENOS
Progesterone - blood
Progesterone Congeners - pharmacology
SECRECION
SECRETION
Sexual Maturation - drug effects
TRANSPLANTATION
TRASPLANTES
Ultrasonography
UTERO
UTERUS
Uterus - anatomy & histology
Vertebrates: reproduction
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Summary:Two experiments were designed to investigate the endocrine mechanisms by which progestin administration induces puberty in heifers. In experiment 1, prepubertal heifers were randomly assigned by age to receive either a single norgestomet implant for 10 days (NORG; n = 15) or to serve as unimplanted controls (CONT; n = 14). Serial blood samples were obtained on Days -0.5, 8.5, and 10.5 (Day 1 day of implant insertion) and were analyzed for concentrations of LH. On Days 9 and 11, 4 heifers in each treatment were slaughtered, and the reproductive tracts were obtained. Weekly progesterone analyses were performed to estimate the day of puberty in heifers not slaughtered. Puberty was induced in 6 of 7 heifers in the NORG treatment, resulting in an earlier (p 0.05) day of puberty in the NORG than in the CONT treatment. The frequency of LH pulses was higher (p 0.05) on Days 8.5 and 10.5 in the NORG as compared to the CONT treatment. Although no difference (p 0.10) was observed between treatments in follicular development, uterine weight was greater (p 0.05) in NORG than in CONT heifers on Day 11. In experiment 2, prepubertal heifers (n
ISSN:0006-3363
1529-7268
DOI:10.1095/biolreprod54.5.1025