title: Intrauterine administration of plant oils inhibits luteolysis in the mare.
abstract: BACKGROUND
  The maternal recognition of pregnancy (MRP) signal in the mare has not been determined, although oestrogens have been proposed as a potential candidate.
  
  
  OBJECTIVE
  To determine effects of intrauterine administration of oestrogen and various oils on cyclic luteolysis in the mare.
  
  
  OBJECTIVE
  Intrauterine oestradiol or fatty acids may suppress luteolysis in the cycling mare when administered during late dioestrus.
  
  
  METHODS
  A single 1 ml dose of slow-release oestradiol (10 mg/ml) in fractionated coconut oil was infused into the uterine lumen of cycling mares on Days 6, 8, 10, 12 or 14 post ovulation (n=12 in each group). Four further groups, each of 12 mares, received an intrauterine infusion of either 1 ml of fractionated coconut oil, peanut oil, mineral oil or a slow-release preparation of oestradiol (10 mg/ml) in mineral oil on Day 10 post ovulation. Serial blood samples were assayed for progesterone concentrations to monitor luteal function.
  
  
  RESULTS
  Intrauterine administration of oestradiol in fractionated coconut oil showed peak efficacy at Day 10 when luteolysis was delayed in 11/12 (92%) mares. The ability of the treatment to delay luteolysis was not significantly different when administered on Days 8 (9/12; 75%), 12 (10/12; 83%) or 14 (6/12; 50%) of dioestrus, but declined significantly when given on Day 6 (3/12; 25%). Oestradiol was not needed to initiate luteostasis since fractionated coconut oil alone or peanut oil administered at Day 10 induced the same high rate of luteal persistence (11/12; 92% for both oils). In contrast, mineral oil did not prolong luteal lifespan, either when administered alone (2/12; 17%) or combined with oestradiol (3/12; 25%).
  
  
  CONCLUSIONS
  These results do not unequivocally rule out a possible involvement of embryonic oestrogens in MRP in the mare but suggest it is unlikely. The results demonstrate that plant oils can postpone luteolysis, suggesting they may modulate synthesis or release of prostaglandins from the mare's endometrium.
  
  
  CONCLUSIONS
  Administration of fractionated coconut or peanut oil on Day 10 post ovulation provides an effective and practical method of prolonging luteal function ('pseudopregnancy') thereby suppressing unwanted oestrous behaviour. Further studies to elucidate the mechanism by which this is achieved may increase understanding of both luteostasis and MRP signal in the mare.
authors.affiliation: The Paul Mellon Laboratory of Equine Reproduction, Newmarket, Suffolk, UK. paulmellonlab@btconnect.com
authors.forename: S
authors.initials: S
authors.lastname: Wilsher
authors.forename: W R
authors.initials: WR
authors.lastname: Allen
mesh_terms: D000818:Animals; D000074263:Coconut Oil; D004333:Drug Administration Routes; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D006736:Horses; D003341:Luteolysis / Q000187:drug effects*; D008899:Mineral Oil / Q000008:administration & dosage / Q000494:pharmacology; D000074241:Peanut Oil; D010938:Plant Oils / Q000008:administration & dosage* / Q000494:pharmacology*; D011247:Pregnancy
chemical_list: D000074241:Peanut Oil; D010938:Plant Oils; D004958:Estradiol; D008899:Mineral Oil; D000074263:Coconut Oil