Long-term effects of porcine zonae pellucidae immunocontraception on ovarian function in feral horses (Equus caballus)

J. F. Kirkpatrick, I. M.K. Liu, J. W. Turner Jnr., R. Naugle, R. Keiper

Research output: Contribution to journalArticle

76 Scopus citations

Abstract

Ten feral mares free-roaming in Maryland, USA, were inoculated with porcine zonae pellucidae (PZP) protein before the breeding season for three consecutive years (1988-90). Ovarian function was monitored for 51 days during the peak of the breeding season after the third annual PZP inoculation, in seven of these males and in four untreated control males, by means of urinary oestrone conjugates and nonspecific progesterone metabolites. None of the ten inoculated mares became pregnant in 1990, compared with 55% of 20 control mares, which included two of the four monitored for ovarian function. Three of the untreated mares demonstrated apparent normal ovarian activity, characterized by preovulatory oestrogen peaks, concurrent progesterone nadirs at ovulation, breeding activity, and luteal-phase progesterone increases after ovulation Two of the seven monitored PZP-treated mares demonstrated ovulatory cycles that did not result in conception. One was pregnant as a result of conception in 1989 and demonstrated a normal, late-gestation, endocrine profile. The remaining four PZP treated mares revealed no evidence of ovulation and urinary oestrogen concentrations were significantly depressed. The experiments indicated that (i) a third consecutive annual PZP booster inoculation is > 90% effective in preventing pregnancies in mares and (ii) three consecutive years of PZP treatment may interfere with normal ovarian function as shown by markedly depressed oestrogen secretion.

Original languageEnglish (US)
Pages (from-to)437-444
Number of pages8
JournalJournal of Reproduction and Fertility
Volume94
Issue number2
DOIs
StatePublished - Jan 1 1992
Externally publishedYes

Keywords

  • Contraception
  • Horse
  • Immunocontraception
  • Oestrogen
  • Ovary
  • Progestin
  • Zona pellucida

ASJC Scopus subject areas

  • Physiology
  • Embryology
  • Molecular Biology
  • Obstetrics and Gynecology
  • Developmental Biology

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