Factors influencing equine chorionic gonadotrophin production in the mare
Article first published online: 19 JAN 2011
© 2011 EVJ Ltd
Equine Veterinary Journal
Volume 43, Issue 4, pages 430–438, July 2011
How to Cite
WILSHER, S. and ALLEN, W. R. (2011), Factors influencing equine chorionic gonadotrophin production in the mare. Equine Veterinary Journal, 43: 430–438. doi: 10.1111/j.2042-3306.2010.00309.x
- Issue published online: 2 JUN 2011
- Article first published online: 19 JAN 2011
- [Paper received for publication 25.06.10; Accepted 09.08.10]
- equine chorionic gonadotrophin (eCG);
- body condition;
Reasons for performing study: 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.
Objectives: 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.
Potential relevance: The results provide insights into some factors that govern the production of the placental gonadotrophin, eCG.