Foaling 101: Poop is Often a Messy, but Important Subject
This may be a “messy” subject, but this time of year foal diarrhea is a common problem on breeding farms with numerous young foals–and it’s a relevant cause for concern as foals can get dehydrated VERY quickly if they stop nursing and have severe diarrhea. Here at Royal Vista Ranches we spend a lot of time and effort differentiating between normal “foal heat diarrhea” and more severe forms of diarrhea. Foals often get diarrhea at 7-14 days of age when the mare experiences her foal heat–this is also the time when the foal is starting to try various solid foods such as hay, grass, grain, etc. These factors and the changing micro flora are often responsible for what we consider “normal” loose feces. Foals with normal “foal heat diarrhea” are bright, alert, and consistently nursing.
Even through this normal foal heat diarrhea, we tend to provide treatment in order to get the foal over it more quickly and to prevent it from getting worse or turning into infectious diarrhea. Most foals respond well to basic medications, and we frequently use Biosponge (made by Platinum) and probiotics, as well as antibiotics, when needed. If a foal has stopped nursing and they are experiencing any form of severe/infectious diarrhea, we closely monitor hydration status and administer IV fluids, as necessary.

There are multiple causes of infectious diarrhea, and we take several preventive measures to avoid foals contracting these infectious types of diarrhea–as prevention is much easier and cost-effective then dealing with a sick foal. Clostridium and Rotavirus can be vaccinated against by immunizing the heavy pregnant mare so that the foal receives antibodies in the colostrum or first milk. We also give the newborn foals an oral antibiotic to prevent Clostridium diarrhea, which can be very severe and can often be fatal. If necessary, we can also administer plasma containing specific antibodies to diarrhea causing agents. 
Keeping this in mind, one thing we suggest and do here at the ranch to ensure that foals are treated and managed in a timely manner is to check mares and foals multiple times a day–making sure that the mare is consistently “nursed out” and not dripping milk or displaying a full/tight bag. Signs like this indicate that the foal may have stopped nursing and could be dehydrated. All foals should be bright, alert, and energetic. Lethargic or “listless” foals are usually a cause for concern as they may be dehydrated and/or running a fever. Infectious diarrhea can present in several forms from an odd color and odor to being very “wet” and almost water-like–this last kind can occasionally be hard to see as it may just look like the foal’s tail is wet. 

Your first line of defense is consistent, close observation. As foal health can change very quickly, it is always best to contact your veterinarian with questions or concerns, and prior to administering any treatment.