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The influence of maternal size on placental, fetal and postnatal growth in the horse. II. Endocrinology of pregnancy.
Abstract: Within-breed artificial insemination and between-breed embryo transfer were carried out in small pony (P) and large Thoroughbred (Tb) mares to create 4 types of horse pregnancy in which the fetus experienced spatial and nutritional deprivation (Tb-in-P; n=8), luxury (P-in-Tb; n=7) or normality (Tb-in-Tb; n=7 and P-in-P; n=7) in utero. Measurement of equine chorionic gonadotrophin (eCG), total conjugated oestrogens and progestagen concentrations in serial peripheral serum samples recovered from all the mares throughout gestation showed that the amount of eCG produced during the first half of gestation was dependent upon the breed of the mare rather than the breed of the fetus being carried. In contrast, the mean total amounts of oestrogens produced, as measured by area under the curve, were significantly greater (P=0.003) in the two types of pregnancy in which a Thoroughbred fetus was being carried (Tb-in-Tb and Tb-in-P) than those in which a pony fetus was gestated (P-in-P and P-in-Tb); the evidence suggests that the Tb fetus may have larger gonads than the P fetus and thereby secrete more C-19 precursor steroids for aromatisation to oestrogens by the placenta. In the final weeks of pregnancy mean plasma progestagen concentrations rose much earlier, and to significantly higher levels (P<0.001), in the Tb-in-P than in the P-in-Tb pregnancies, thereby reflecting the increased fetal stress in the former causing premature maturation of the fetal adrenal gland. This, in turn, resulted in increased secretion of pregnenolone by the adrenal cortex for conversion to progestagens by the placenta.
Publication Date: 2002-02-09 PubMed ID: 11834441DOI: 10.1677/joe.0.1720237Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research explores how the size of a horse maternal breed influences hormonal changes during pregnancy. The study showed that various hormonal concentrations during pregnancy depend on the breed of the mare and the breed of the fetus.
Experiment Setup
- The experiment was established using within-breed artificial insemination and between-breed embryo transfer.
- The horses chosen for the experiment were small pony mares (P) and large Thoroughbred mares (Tb) to form four types of horse pregnancy. The categories were designed in such a manner that the unborn horse either experienced spatial and nutritional deprivation, luxury, or normality while in the womb.
Hormonal Monitoring and Discoveries
- Throughout the gestation period, samples of peripheral serum were taken from all mares. Three types of hormones were focused on in the measurements: equine chorionic gonadotrophin (eCG), total conjugated oestrogens and progestagen.
- The researchers discovered that the amount of eCG produced in the first part of gestation relied on the mare’s breed, not the fetus breed. Conversely, the total amounts of oestrogens produced were significantly higher when a Thoroughbred fetus was gestated irrespective of the breed of the mare. This suggests that a Tb fetus might have larger gonads than a P fetus, thus leading to the secretion of more C-19 precursor steroids, which then convert to oestrogens in the placenta.
- In the last weeks of gestation, plasma progestagen concentrations rose much earlier, to significantly higher levels in Tb-in-P than in P-in-Tb pregnancies, indicating increased fetal stress in the former. This stress caused premature maturation of the fetal adrenal gland, leading to an increased secretion of pregnenolone, which the placenta converts to progestagens.
Implications
- The study offers insights for breeders, veterinary specialists, and researchers working with horse breeding.
- Understanding the hormonal changes that occur as a result of the interaction between different mare and fetus breeds can be critical in the management of horse pregnancies and the postnatal health of the foals.
- The findings suggest that the physiological demands of a fetus can potentially be met differently depending on the size of the mare carrying it, thus affecting the fetus’s growth and development.
Cite This Article
APA
Allen WR, Wilsher S, Stewart F, Stewart F, Ousey J, Ousey J, Fowden A.
(2002).
The influence of maternal size on placental, fetal and postnatal growth in the horse. II. Endocrinology of pregnancy.
J Endocrinol, 172(2), 237-246.
https://doi.org/10.1677/joe.0.1720237 Publication
Researcher Affiliations
- Thoroughbred Breeders' Association Equine Fertility Unit, Mertoun Paddocks, Woodditton Road, Newmarket, Suffolk CB8 9BH, UK.
MeSH Terms
- Analysis of Variance
- Animals
- Animals, Newborn / growth & development
- Body Constitution / physiology
- Breeding
- Embryo Transfer / veterinary
- Embryonic and Fetal Development / physiology
- Enzyme-Linked Immunosorbent Assay / methods
- Estrogens, Conjugated (USP) / blood
- Female
- Gestational Age
- Gonadotropins, Equine / blood
- Horses / physiology
- Insemination, Artificial
- Placentation
- Pregnancy
- Pregnancy, Animal / metabolism
- Progestins / blood
Citations
This article has been cited 8 times.- Nagel C, Melchert M, Aurich C, Aurich J. Differences in Endocrine and Cardiac Changes in Mares and Her Fetus before, during, and after Parturition in Horses of Different Size. Animals (Basel) 2020 Sep 4;10(9).
- Peugnet P, Robles M, Mendoza L, Wimel L, Dubois C, Dahirel M, Guillaume D, Camous S, Berthelot V, Toquet MP, Richard E, Sandersen C, Chaffaux S, Lejeune JP, Tarrade A, Serteyn D, Chavatte-Palmer P. Effects of moderate amounts of barley in late pregnancy on growth, glucose metabolism and osteoarticular status of pre-weaning horses. PLoS One 2015;10(4):e0122596.
- Pomeroy E, Wells JC, Cole TJ, O'Callaghan M, Stock JT. Relationships of maternal and paternal anthropometry with neonatal body size, proportions and adiposity in an Australian cohort. Am J Phys Anthropol 2015 Apr;156(4):625-36.
- Macdonald EM, Koval JJ, Natale R, Regnault T, Campbell MK. Population-based placental weight ratio distributions. Int J Pediatr 2014;2014:291846.
- Wells JC, Sharp G, Steer PJ, Leon DA. Paternal and maternal influences on differences in birth weight between Europeans and Indians born in the UK. PLoS One 2013;8(5):e61116.
- Manso Filho HC, Costa HE, Wu G, McKeever KH, Watford M. Equine placenta expresses glutamine synthetase. Vet Res Commun 2009 Feb;33(2):175-82.
- Adams AP, Oriol JG, Campbell RE, Oppenheim YC, Allen WR, Antczak DF. The effect of skin allografting on the equine endometrial cup reaction. Theriogenology 2007 Jul 15;68(2):237-47.
- Allen WR. Ovulation, pregnancy, placentation and husbandry in the African elephant (Loxodonta africana). Philos Trans R Soc Lond B Biol Sci 2006 May 29;361(1469):821-34.
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