Sensitivity of sheep to exogenous prostaglandin F early in the estrous cycle

W. F. Pope*, H. Cárdenas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

One hundred ewes were monitored twice-a-day for estrus and only those ewes displaying an estrous cycle of 16.5-18.0 days in length were utilized in the experiment. Ewes were subsequently treated with a single injection of 5 or 10 mg of prostaglandin F (PGF) on days 3.0, 3.5, 4.0, 4.5 or 5.0 (n=10 ewes per day) of the estrous cycle (day 0.0=the a.m. or p.m. of first detected estrus) to determine their sensitivity to induction of estrus with prostaglandin F. Ewes that were detected in estrus within 24-72 h after treatment with PGF were considered sensitive to PGF treatment. This definition of sensitivity to PGF was inclusive as all ewes either responded within 24-72 h after PGF treatment or they came into estrus at the expected time based on their previous, untreated, estrous cycle. Results indicated that a significant (P<0.05) proportion of ewes became sensitive to the induction of estrus with PGF between days 3.5 and 4.0, as 10 and 50% of the ewes, respectively, responded to treatment. PGF treatment on days 4.5 and 5.0 caused a non-significant increase in responsiveness as 70 and 75% of the ewes, respectively, came into estrus within 1-3 days. The 10 mg dose, being more effective than the 5 mg dose, shifted the response curve by roughly 20 percentage points beginning on day 3.5 and continued through the later exposure times. In conclusion, the CL early in the estrous cycle of ewes was variable in its responsive to a single exposure to PGF and some of this variability was attributed to physiological events occurring between days 3.5 and 4.0.

Original languageEnglish (US)
Pages (from-to)245-248
Number of pages4
JournalSmall Ruminant Research
Volume55
Issue number1-3
DOIs
StatePublished - Oct 2004

Keywords

  • Estrous cycle
  • Estrus
  • Prostaglandin
  • Sheep

ASJC Scopus subject areas

  • Food Animals
  • Animal Science and Zoology

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