title: Factors influencing equine chorionic gonadotrophin production in the mare.
abstract: BACKGROUND
  An opportunity to monitor equine chorionic gonadotrophin (eCG) production during 61 pregnancies in 25 Thoroughbred mares mated to the same Thoroughbred stallion was utilised in order to further knowledge regarding factors involved in the production of this hormone.
  
  
  OBJECTIVE
  To examine the effects of maternal body condition, exercise and parity on eCG production.
  
  
  METHODS
  In the first experiment, maiden mares were fed either a moderate (n = 9) or an excessive (n = 10) food intake throughout gestation. In the second experiment, 5 mares were exercised daily during pregnancy and eCG production rates were compared to 5 nonexercised mares. In the third experiment, eCG profiles were compared in 9 mares during 3 successive pregnancies. Equine chorionic gonadotrophin secretion was assessed as area under the curve (AUC), peak serum concentration, timing of the peak and the rate of decline. In addition, a mean eCG profile of 61 pregnancies was created to provide means and ranges for the above parameters.
  
  
  RESULTS
  In Experiment 1, eCG production was significantly higher in moderately rather than excessively fed mares in terms of AUC and peak eCG concentrations. In Experiment 2, the mean AUC did not differ between exercised and nonexercised animals but mean eCG concentrations were significantly higher in nonexercised mares between Days 60 and 90 of gestation. In Experiment 3, eCG became undetectable significantly earlier in gestation in the third parity. The mean eCG profile of 61 pregnancies showed a peak of 64.5 ± 3.7 iu/ml at 62.4 ± 1.0 days after ovulation and was undetectable by 134.1 ± 1.7 days. Peak eCG levels reduced by 50% 22.6 ± 1.13 days.
  
  
  CONCLUSIONS
  Some of the factors examined clearly influenced eCG production rate, the secretion of this hormone and its rate of disappearance from the blood.
  
  
  CONCLUSIONS
  The results provide insights into some factors that govern the production of the placental gonadotrophin, eCG.
authors.affiliation: The Paul Mellon Laboratory of Equine Reproduction, Cheveley Park, Newmarket, UK. sandrawilsher@hotmail.co.uk
authors.forename: S
authors.initials: S
authors.lastname: Wilsher
authors.forename: W R
authors.initials: WR
authors.lastname: Allen
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology; D006063:Chorionic Gonadotropin / Q000097:blood / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D005260:Female; D006736:Horses / Q000097:blood / Q000502:physiology*; D010298:Parity / Q000502:physiology*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011247:Pregnancy
chemical_list: D006063:Chorionic Gonadotropin