Horses - Diet and Nutrition/The winter runs


We have two older geldings, both retired show horses.  During the summer, we supplement pasture grass with timothy hay and a senior-horse grain supplement.  Every winter after we bring the horses in off the pastures, our 16 year old appie gelding gets the runs.  We have increased the amount of timothy hay they get to off-set the pasture grass and have added a small amount of alfalfa pellets as well.  We are still feeding the same grain supplement as before.  Is something in this mix causing him to have the runs or do we need to include something that acts as a binder?  He does not have the runs during the summer months when he is eating grass.

Hello Sanda,

Thank you for your question.  Diarrhea in horses can be caused by so many factors and change in diet, especially changes in forage, can be one of the many causes.  Because forages (pasture and hay) are fermented by bacteria in the cecum of the horse, and each type of forage requires a different type of bacteria to ferment it, changing forage types quickly can leave your horse in a period of adjustment where he is not fermenting the new forage properly and the result can be diarrhea.  In more northern climates where grazing horses go through changes in diet from quality pasture to frost damaged forages to dry hay, there certainly can be instances of digestive upset.  Most of these related issues will resolve themselves over time, and you can help ease the symptoms by feeding a quality probiotic through the transition.  A probiotic like Alltech's LifeForce Formula will help improve digestive efficiency and promote the growth of beneficial bacteria making the transition of forages easier on your horse. The type of diet you are describing should not in itself cause diarrhea...just make sure that you phase your new forages in slowly over a 7-10 day time frame to avoid further gastric irritation.

Mold or fungus in your hay could cause diarrhea so perhaps a closer examination of your forage quality can tell you if it is the root of the problem.  If your hay has mold on it, you should not feed it at all.  Mold generates myctoxins that can destroy essential cecal bacteria, again leaving your horse unable to properly ferment the forages.  Mycotoxins can also cause systemic metabolic disorders, so avoid feeding contaminated feeds of any kind.  The midwest US is reporting high mycotoxin levels in corn this year as a result of the drought stress during the growing season so avoid feeding mycotoxin-prone cereal grains this fall.

If, however, diarrhea persists beyond a few weeks (to a month in older horses) I would suggest you have your vet out to take a look.  There are some more serious illnesses that can cause chronic or acute diarrhea that can be treated.  The danger with diarrhea of course is dehydration, and long lasting dehydration can lead to a variety of metabolic disorders that are best prevented, and are preventable with treatment.  Again, your vet would better be able to help you with this.

Thanks, Corlena

Horses - Diet and Nutrition

All Answers

Answers by Expert:

Ask Experts


Corlena Patterson


I can help with any of your horse nutrition questions and concerns. I have been involved with horses for closing on 40 years, with a B.Sc in Animal Science and currently working on an M.Sc in Equine Science with the University of Edinburgh. I have owned my own feed store, consulted professionally as an equine nutritionist, and lectured in the fields of equine and dairy nutrition at the University level for 5 years. I have developed and currently market 'Ration-X', a ration formulation program for horses...designed for the everyday horse owner. I am happy to help in any way I can.


Experienced in developing and implementing feed programs for horses of all disciplines, creating custom horse supplements and managing inter-disciplinary equine facilities. Specialize in equine nutrition consulting.

The American Society of Equine Appraisers

'Stable Management' Handbook, Equine Canada.

M.Sc (Equine Science-current), B.Sc(Agr) Animal Science, Equine Sports Massage Therapy Certification, Farrier Certification, Equine Consultant Certification, Certified Equine Appraiser, Certified in Emergency Equine Rescue.

©2017 All rights reserved.