Manure Eating in Adult Horse

We have a seven-year-old draft cross gelding who was treated for Lyme disease in October of 2000 with 8 grams of doxycycline (a broad-spectrum tetracycline antibiotic) twice daily for three weeks. Since that time, and not previously, we have witnessed him eating fresh manure of his pasture mates. We presumed that daily probiotics (Accel) would restore the gut flora, which we assumed he was lacking and was attempting to restore to his gut through eating manure. His diet is--and always has been--very well balanced. Can you offer any explanation for the continued coprophagy?


I don't really have an answer to this one. There have been no controlled studies on the effects of oral antibiotics on a horse's gut microflora, although it is assumed that prolonged use of oral antibiotics will have an impact. The microbial population of a horse's gut is very complex and varied, much more so than the commercially available "probiotics." The normal coprophagy observed in young foals (two to three weeks old) has been hypothesized to be in response to their need to establish a balanced microbial population, but this has never been proven (to my knowledge). Coprophagy in adult horses has only been reported in response to starvation (not the case in this horse, apparently) or possibly mineral deficits. If he has a balanced ration and free access to trace mineral salt, I would guess that he might be lacking a component of his gut microflora that is not provided in the probiotics. I wouldn't worry too much as long as the other horses are on a good deworming program and he is not showing other signs of deficiency (weight loss, poor hair coat, lack of energy, etc).

About the Author

Sarah Ralston, VMD, PhD, Dipl. ACVN

Sarah L. Ralston, VMD, PhD, Dipl. ACVN, is a professor in the Department of Animal Sciences at Rutgers' School of Environmental and Biological Sciences, specializing in equine nutrition. Her research has focused on the effects of diet on metabolism, behavior, and the development of orthopedic disease in young horses, and she has additional interests in nutritional modulation of stress, metabonomics (the study of metabolic responses to drugs, environmental changes, and diseases), and pasture management. Previous research highlights were the pioneering work she did in nutrition for geriatric horses and post-surgical colics while at Colorado State University in the 1980s and the discovery of the correlation of hyperinsulinemia with development of osteochondrosis in young Standardbreds.

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