Coprophagy: Conventional Conduct?

Q: I would like to query the concept of foals eating mare excrement. I breed horses and believe I have excellent animal husbandry. To date I have only ever witnessed two foals eating mare waste. To date I have bred over 1,000 foals with a loss of two due to injury. My belief is if a mare has been given a balanced diet with correct minerals, trace elements, salts, amino acids, etc., etc. while pregnant, the foal will naturally have a well-balanced system at birth. The foal will take its immunity via the colostrum or, in a worst-case scenario, plasma transfer, giving it the protection needed to sustain a healthy life. Pre/probiotics will be present in the colostrum and milk flow. I can understand a foal eating waste if the mare is not producing quality milk or colostrum. Why should it be classed as normal behavior when the foal is obviously lacking some nutrient or other?

Gina Hawkins, via e-mail

A: Coprophagy, as it is known, is classified as a normal behavior because every time the behavior of foals, healthy or not, has been observed carefully for a good length of time, whether by behaviorists, animal scientists, or veterinarians, coprophagy is seen to occur during the window of as early as one week of age until about two months of age. The results have been consistent and predictable, just like running in circles around the dam from Day 1 to a couple of weeks, or sleeping flat out for longer periods than adults until 12 months, or performing an extraordinary amount of self-grooming for the first two days of life. Beyond these consistent observations, this behavior occurs in association with beginning to ingest foods other than the dam’s milk. The behavior also has a plausible explanation as a functional aspect of normal digestive development.

There are actually several hypotheses as to a positive function, and one of those is a pretty well-accepted explanation. Ingestion of the adult feces populates the foal’s digestive tract with bacteria necessary to digest the new foods to which it is exposed. The feces are usually from the dam, or at least another adult in the herd, which nicely delivers the bacteria best suited for digesting the forages in the foal’s local environment. Veterinary medical books on rearing orphan foals recommend providing an orphan with the manure of an adult horse so that this normal process can take place.

If you would like to read more about it, you can go to Google Scholar and search “horse, foal, coprophagia.” You will find a copy of the 1984 scientific paper from Japan describing the study of the appearance of the good digestive bacteria within about four days of eating the feces and at the time they start foraging. You can also find a chapter by Gary Magdesian, DVM, Dipl. ACVIM, ACVECC, ACVP (of the University of California, Davis), from a book by Laurie Cage called Hand-Rearing Wild and Domestic Animals, describing the importance of coprophagy to foal health. Magdesian recommends providing an orphan foal with some adult feces to ingest. Otherwise it will eat its own feces, which do not have the bacteria it needs, and it can cause some adverse consequences without the benefits.

About the Author

Sue McDonnell, PhD, Certified AAB

Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.

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