Effects of temporary calf removal and osmotic pump delivery of gonadotropin-releasing hormone on synchronized estrus, conception to a timed artificial insemination and gonadotropin secretion in norgestomet-estradiol valerate-treated cattle

Walter Roland McVey, Jr., G. L. Williams

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The objective of this study was to determine whether a constant, lowdose infusion of gonadotropin-releasing hormone (GnRH) following norgestomet-estradiol valerate estrus synchronization (SMB) and temporary calf removal (CR) would enhance fertility to a timed, 48-h artificial insemination (AI) in cattle. A subcutaneous osmotic pump was employed to deliver approximately 2.5 μg GnRH per hour for 6 to 7 d following norgestomet implant removal. In Experiment 1, suckled Brahman crossbred cows (n = 221) were assigned randomly to one of four treatments: 1) SMB (n = 58); 2) SMB+48-h CR (SMB+CR, n = 55); 3) SMB+GnRH (n = 56); and 4) SMB+CR+GnRH (n = 52). Virgin heifers (n = 69), 12 to 14 months of age, were allotted to Treatments 1 and 3. The CR (cows) and GnRH (cows and heifers) treatments began at SMB implant removal and all females were inseminated 48 h later. Experiment 2 assessed luteinizing hormone (LH) secretion following SMB implant removal and(or) osmotic pump insertion in 44 cyclic cows (n = 11/treatment group) treated as in Experiment 1. Cows received SMB treatment either early (Days 3 to 5) or late (Days 11 to 15) in the estrous cycle (n = 22/period). Conception rate at timed AI for SMB+CR was superior (50.9%; P<0.025) to all other treatments (SMB, 27.5%; SMB+GnRH, 26.9%; SMB+CR+GnRH, 26.9%). Gonadotropin-releasing hormone attenuated the positive effects of CR by reducing (P<0.02) cumulative pregnancy rates on Day 24 in SMB+CR+GnRH cows. Conception at timed AI in virgin SMB heifers (52.9%) was higher (P<0.025) than SMB+GnRH heifers (25.7%), and it remained higher (P<0.05) on Day 24 (85.3% vs 60.0%). Gonadotropin-releasing hormone stimulated a premature, preovulatory-like surge of LH which peaked 6.8±0.6 h following pump insertion. As employed here, GnRH reduced fertility by disrupting the normal sequence of endogenous endocrine events in progestogen-primed females.

Original languageEnglish (US)
Pages (from-to)969-978
Number of pages10
JournalTheriogenology
Volume32
Issue number6
DOIs
StatePublished - Jan 1 1989

Fingerprint

estradiol valerate
norgestomet
Artificial Insemination
Estrus
gonadotropin-releasing hormone
gonadotropins
Gonadotropins
artificial insemination
Gonadotropin-Releasing Hormone
pumps
estradiol
estrus
secretion
calves
cattle
cows
heifers
luteinizing hormone
Luteinizing Hormone
Fertility

All Science Journal Classification (ASJC) codes

  • Small Animals
  • Food Animals
  • Animal Science and Zoology
  • Equine

Cite this

@article{6239c7b8a62140908be088efe8edba4b,
title = "Effects of temporary calf removal and osmotic pump delivery of gonadotropin-releasing hormone on synchronized estrus, conception to a timed artificial insemination and gonadotropin secretion in norgestomet-estradiol valerate-treated cattle",
abstract = "The objective of this study was to determine whether a constant, lowdose infusion of gonadotropin-releasing hormone (GnRH) following norgestomet-estradiol valerate estrus synchronization (SMB) and temporary calf removal (CR) would enhance fertility to a timed, 48-h artificial insemination (AI) in cattle. A subcutaneous osmotic pump was employed to deliver approximately 2.5 μg GnRH per hour for 6 to 7 d following norgestomet implant removal. In Experiment 1, suckled Brahman crossbred cows (n = 221) were assigned randomly to one of four treatments: 1) SMB (n = 58); 2) SMB+48-h CR (SMB+CR, n = 55); 3) SMB+GnRH (n = 56); and 4) SMB+CR+GnRH (n = 52). Virgin heifers (n = 69), 12 to 14 months of age, were allotted to Treatments 1 and 3. The CR (cows) and GnRH (cows and heifers) treatments began at SMB implant removal and all females were inseminated 48 h later. Experiment 2 assessed luteinizing hormone (LH) secretion following SMB implant removal and(or) osmotic pump insertion in 44 cyclic cows (n = 11/treatment group) treated as in Experiment 1. Cows received SMB treatment either early (Days 3 to 5) or late (Days 11 to 15) in the estrous cycle (n = 22/period). Conception rate at timed AI for SMB+CR was superior (50.9{\%}; P<0.025) to all other treatments (SMB, 27.5{\%}; SMB+GnRH, 26.9{\%}; SMB+CR+GnRH, 26.9{\%}). Gonadotropin-releasing hormone attenuated the positive effects of CR by reducing (P<0.02) cumulative pregnancy rates on Day 24 in SMB+CR+GnRH cows. Conception at timed AI in virgin SMB heifers (52.9{\%}) was higher (P<0.025) than SMB+GnRH heifers (25.7{\%}), and it remained higher (P<0.05) on Day 24 (85.3{\%} vs 60.0{\%}). Gonadotropin-releasing hormone stimulated a premature, preovulatory-like surge of LH which peaked 6.8±0.6 h following pump insertion. As employed here, GnRH reduced fertility by disrupting the normal sequence of endogenous endocrine events in progestogen-primed females.",
author = "{McVey, Jr.}, {Walter Roland} and Williams, {G. L.}",
year = "1989",
month = "1",
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doi = "10.1016/0093-691X(89)90506-2",
language = "English (US)",
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journal = "Theriogenology",
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T1 - Effects of temporary calf removal and osmotic pump delivery of gonadotropin-releasing hormone on synchronized estrus, conception to a timed artificial insemination and gonadotropin secretion in norgestomet-estradiol valerate-treated cattle

AU - McVey, Jr., Walter Roland

AU - Williams, G. L.

PY - 1989/1/1

Y1 - 1989/1/1

N2 - The objective of this study was to determine whether a constant, lowdose infusion of gonadotropin-releasing hormone (GnRH) following norgestomet-estradiol valerate estrus synchronization (SMB) and temporary calf removal (CR) would enhance fertility to a timed, 48-h artificial insemination (AI) in cattle. A subcutaneous osmotic pump was employed to deliver approximately 2.5 μg GnRH per hour for 6 to 7 d following norgestomet implant removal. In Experiment 1, suckled Brahman crossbred cows (n = 221) were assigned randomly to one of four treatments: 1) SMB (n = 58); 2) SMB+48-h CR (SMB+CR, n = 55); 3) SMB+GnRH (n = 56); and 4) SMB+CR+GnRH (n = 52). Virgin heifers (n = 69), 12 to 14 months of age, were allotted to Treatments 1 and 3. The CR (cows) and GnRH (cows and heifers) treatments began at SMB implant removal and all females were inseminated 48 h later. Experiment 2 assessed luteinizing hormone (LH) secretion following SMB implant removal and(or) osmotic pump insertion in 44 cyclic cows (n = 11/treatment group) treated as in Experiment 1. Cows received SMB treatment either early (Days 3 to 5) or late (Days 11 to 15) in the estrous cycle (n = 22/period). Conception rate at timed AI for SMB+CR was superior (50.9%; P<0.025) to all other treatments (SMB, 27.5%; SMB+GnRH, 26.9%; SMB+CR+GnRH, 26.9%). Gonadotropin-releasing hormone attenuated the positive effects of CR by reducing (P<0.02) cumulative pregnancy rates on Day 24 in SMB+CR+GnRH cows. Conception at timed AI in virgin SMB heifers (52.9%) was higher (P<0.025) than SMB+GnRH heifers (25.7%), and it remained higher (P<0.05) on Day 24 (85.3% vs 60.0%). Gonadotropin-releasing hormone stimulated a premature, preovulatory-like surge of LH which peaked 6.8±0.6 h following pump insertion. As employed here, GnRH reduced fertility by disrupting the normal sequence of endogenous endocrine events in progestogen-primed females.

AB - The objective of this study was to determine whether a constant, lowdose infusion of gonadotropin-releasing hormone (GnRH) following norgestomet-estradiol valerate estrus synchronization (SMB) and temporary calf removal (CR) would enhance fertility to a timed, 48-h artificial insemination (AI) in cattle. A subcutaneous osmotic pump was employed to deliver approximately 2.5 μg GnRH per hour for 6 to 7 d following norgestomet implant removal. In Experiment 1, suckled Brahman crossbred cows (n = 221) were assigned randomly to one of four treatments: 1) SMB (n = 58); 2) SMB+48-h CR (SMB+CR, n = 55); 3) SMB+GnRH (n = 56); and 4) SMB+CR+GnRH (n = 52). Virgin heifers (n = 69), 12 to 14 months of age, were allotted to Treatments 1 and 3. The CR (cows) and GnRH (cows and heifers) treatments began at SMB implant removal and all females were inseminated 48 h later. Experiment 2 assessed luteinizing hormone (LH) secretion following SMB implant removal and(or) osmotic pump insertion in 44 cyclic cows (n = 11/treatment group) treated as in Experiment 1. Cows received SMB treatment either early (Days 3 to 5) or late (Days 11 to 15) in the estrous cycle (n = 22/period). Conception rate at timed AI for SMB+CR was superior (50.9%; P<0.025) to all other treatments (SMB, 27.5%; SMB+GnRH, 26.9%; SMB+CR+GnRH, 26.9%). Gonadotropin-releasing hormone attenuated the positive effects of CR by reducing (P<0.02) cumulative pregnancy rates on Day 24 in SMB+CR+GnRH cows. Conception at timed AI in virgin SMB heifers (52.9%) was higher (P<0.025) than SMB+GnRH heifers (25.7%), and it remained higher (P<0.05) on Day 24 (85.3% vs 60.0%). Gonadotropin-releasing hormone stimulated a premature, preovulatory-like surge of LH which peaked 6.8±0.6 h following pump insertion. As employed here, GnRH reduced fertility by disrupting the normal sequence of endogenous endocrine events in progestogen-primed females.

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