Introduction

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Results and
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Conclusion/
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Future Research
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Background

Water intake and confinement effects on estrogen and cortisol production in pregnant mares

Carmelita Lamb, R.M. Weigl, and J.E. Tilton
Department of Animal and Range Sciences
North Dakota State University


Abstract
Daily aliquots of mare urine were collected to determine the secretory patterns of estradiol (E₂) and cortisol in confined pregnant mares exposed to different levels of water intake and exercise. Sixty-five mid-gestation (days to 150-200 of pregnancy) mares were randomly assigned to one of three treatment groups. Group I (n=25) mares remained confined at all times with restricted water intake (7 gal/mare/day). Group II (n=25) mares were allowed free exercise for one hour each day with restricted water intake (7 gal/mare/day). Group III (n=15) mares were confined with ad libitum access to water. Urine aliquots (8 ml) were drawn daily at 1000 h for a 14 day period from a 12 hour pooled sample. Urinary E₂ data were reported in ng/mg creatinine to normalize for urinary dilution difference between individual mares. Watering strategies influenced urinary E₂ concentrations in pregnant mares that had free access to water at all times. Unlimited access to water increased (P<.001) rather than decreased urinary E₂ concentrations. Urinary cortisol concentrations were lower (P<.05) in confined mares (Group I) than in exercised mares (Group II), indicating no adverse effect of extensive confinement in the pregnant mare. Urinary cortisol concentrations were not affected (P>.05) by water intake. The results suggest that confinement of the mare is not stressful and that free access to water may potentially benefit the estrogen producing capability of the pregnant mare. This article is only available online at http://www.ag.ndsu.nodak.edu/ndagres/ndagres.htm

Impact — The results of this study indicate that restriction of water intake in pregnant mares used for collection of urine for estrogen processing is unfounded and may in fact limit production of the desired estrogenic substances and that confinement of mares is not stressful to the extent of causing elevated urinary cortisol concentrations.
Audience — Horsemen, county agents, reproductive scientists.

Keywords
stress, exercise, urine, estrogens, mares, cortisol

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