Fescue toxicosis affects horses that graze on endophyte-infected tall fescue grass. The endophyte produces ergovaline, a toxin that disrupts hormone levels and can cause agalactia in pregnant mares. Studies examined mares treated with bromocriptine to mimic ergovaline's effects, finding decreased prolactin and progesterone levels. Mares treated with the D2 receptor antagonist domperidone saw increased prolactin and progesterone, showing it effectively treats fescue toxicosis. However, an agalactic mare from Japan had very low prolactin but normal progesterone, indicating its condition differs from typical fescue toxicosis and may not respond to domper

1. RESEARCH POSTER PRESENTATION DESIGN © 2012
www.PosterPresentations.com
Fescue toxicosis is an ongoing challenge within the USA
where in 2011 over 35 million acres were made up of endophyte-
infected tall fescue grass and more than 700,000 horses
consumed it as their primary forage. The endophyte, a type of
fungus, has a symbiotic relationship with a host plant. The fescue
grass provides shelter and protection while the endophyte helps
the host plant collect a greater amount of nutrients. The host plant
and the endophyte can produce toxins such as ergovaline which
has been linked to cause symptoms of fescue toxicosis such as
agalactia which is characterized by a lack of udder development
and milk production in pregnant mares. Ergovaline is a D₂-
dopamine receptor agonist which inhibits estrogens from binding
to their proper receptors causing the body to produce a greater
amount of estrogen. Normally 30-40 days before parturition
(birth) progestogen levels should increase and 5-10 days before
parturition prolactin levels should increase. Estrogen levels
should decrease before prolactin levels increase. In cases of
fescue toxicosis, progestogen and prolactin levels are much lower
than needed for proper development while estrogen levels are too
high. In Japan there has been an ongoing issue with mares
developing agalactia. Considering that the common cause for
agalactia in the USA is fescue toxicosis, agalactic mares in Japan
have been tested to see if fescue toxicosis or something like it
may be the cause. If the agalactia is caused by fescue toxicosis,
then domperidone treatment may be used to relieve some of the
symptoms.
Abstract
Objectives
The Endocrine Disruptive Effects of Ergopeptine Alkaloids on
Pregnant Mares
Evans, Tim J. © 2011
 Mares are treated with bromocriptine
• Bromocriptine, a semi-synthetic alkaloid, acts
similarly to ergovaline by blocking D₂-dopamine
receptors
 Mares treated with domperidone therapy
• Domperidone is a D₂-dopamine receptor antagonist
which allows the estrogen to attach to its proper
receptors
 Mares treated with reserpine
• Depletes brain levels of dopamine, serotonine, and/or
norepinephrine
Procedures
Bromocriptine Treatment Causes Decrease in PRL
& PRG Concentrations
Results
Conclusion
Bromocriptine is used to mimic the effects of
ergovaline. The presence of bromocriptine caused a
decrease in PRL & PRG concentrations.
Domperidone therapy is effective in treatment of
fescue toxicosis in typical cases.
However, only a low concentration of PRL is
recognized within the agalactic mare from Japan.
This indicates that something other than ergovaline
must be causing agalactia in this particular mare.
Since the pathology in which agalactia is caused
within the mare is different from the pathology seen
within fescue toxicosis, it is less likely that
domperidone therapy will be as effective. Currently
the cause of agalactia in the case from Japan is
unknown.
References
Evans, T. J. (2011). The Endocrine Disruptive Effects of Ergopeptine Alkaloids on
Pregnant Mares. Veterinary Clinics of North America: Equine Practice, 165-173.
Herron, C. (2015). Domperidone Therapy in the Fight Against Fescue Toxicosis.
Senior Honors Thesis.
Korosue, K., et al. (2013). Changes in Serum Concentrations of Prolactin,
Progestagens, and Estradiol-17ß and Biochemical Parameters During Peripartum in an
Agalactic Mare. Journal of Equine Veterinary Science, 279-286.
Neotyphodium coenophialum. (2012, December 21). Retrieved March 23, 2015,
from Microbe Wiki: https://microbewiki.kenyon.edu/index.php/Neotyphodium_coenophialum
Nevala, R. (2001). Isoflavones. Effects of genistein and daidzein on arterial tone and
blood pressure in rats.
Acknowledgements
The author thanks Dr. Laura Ong and Dr. Kelly Vaughan for their
involvement editing this presentation. The author also thanks the Biology
Department at King University for funding this project. This presentation is an
extension of Chelsea Herron’s Senior Honors Thesis (2015).
• Determine the general pathology of fescue
toxicosis
• Discover what is effective for treatment of
fescue toxicosis
• Determine if the agalactic mares in Japan are
suffering from fescue toxicosis
Presented by: Chelsea Herron
Fescue Toxicosis:
Disruption of Pregnant Mare Endocrine Systems by Ergopeptine Alkaloids
Figure 4 Weekly changes in serum concentrations of
progestagens from a period of 10 weeks before parturition to
a week after parturition in the agalactic mare, compared with
those of the control mares (Korosue, Kenji et al., 2013).
Figure 3 Daily changes in serum prolactin concentrations
from 10 days before parturition to the day after parturition in
the agalactic mare, compared with those of the control mares
(Korosue, Kenji et al., 2013).
Figure A shows the underdeveloped udder of
an agalactic mare. Figure B shows the normal
udder development expected for a pregnant
mare 2-6 weeks before parturition (Korosue,
Kenji et al., 2013).
Figure C Ergot alkaloid ergovaline from
endophyte Neotyphodium coenophialum
associated with the effects of fescue
toxicosis. A D₂-dopamine receptor agonist
(Neotyphodium coenophialum, 2012).
Figure D Estradiol-17ß: a hormone that
should decrease before the pronounced
increase of prolactin 5-10 days before
parturition (Nevala, Riikka, 2001).
Changes in Serum Concentrations of Prolactin, Progestagens,
and Estradiol-17ß and Biochemical Parameters During Peripartum in
an Agalactic Mare
Korosue, Kenji et al. © 2013
 Hormone levels are determined for the normal mares
 Hormone levels are determined for the agalactic mare
• Blood taken and analyzed
• Primary hormones: PRL, PRG, 17ß-estradiol
Figure 1a prolactin (PRL) concentrations after bromocriptine
treatment. Figure 1b progestagen (PRG) concentrations after
bromocriptine treatment. Both PRL & PRG are significantly
low compared to the control group depicted by asterisk lines
(Evans, Tim J., 2011).
Figure 2a PRL concentrations after domperidone therapy
depicted by asterisk line. PRL concentrations after reserpine
therapy depicted by triangles. Figure 2b PRG concentrations
after therapy depicted by asterisk line. PRG concentrations
after reserpine therapy depicted by triangles (Evans, Tim J.,
2011).
In both studies prolactin concentrations were considerably
lower than normal. The first study showed a significant decrease in
progesterone, but the second study had relatively normal levels of
progesterone.
Agalactia vs. Normal Development
Progestagens(ng/ml)
Fig. 1a Fig. 1b
Fig. 2a Fig. 2b
Domperidone Therapy Causes Increase in PRL &
PRG Concentrations
Low Concentration of PRL in Agalactic Mare
Relatively Normal Concentration of PRG in
Agalactic Mare
Diagram of Ergovaline
Diagram of Estradiol-17ß