Secretory diarrhea is the nightmare of every nutritionist, especially when it leads to secondary pathogenic complications that require veterinary intervention. At the end, as both forms of diarrhea are extremely common and the former often leads to the latter, the distinction is often lost in the minds of most; the more so as both frequently end up in the application of antibiotics.
Secretory diarrhea, by its very nature, is not pathogenic as no microorganism is responsible for its development. Instead, it is the composition of feed that causes excessive water leakage from the enteric epithelium into the gut lumen. Such can be the case when the feed contains excessive amounts of common salt (sodium chloride), high levels of potassium or sulfur, or “ash” in general. Another case can be that of simple sugars. For example, table sugar and lactose are two very well-known laxatives, and they owe this trait to the excessive water secretion they cause. Indeed, both sugars are characterized as hydrophilic, in that they attract water in general. Evidence to this effect is the frequent caked appearance in the warehouse of bags containing dextrose (another simple sugar) that require shaking before emptying to break up the conglomerates of sugar due to water absorption. Excess protein will not cause secretory diarrhea, but will cause excessive water consumption and urine excretion. This might be confused with secretory diarrhea (or watery feces) only in poultry.
The basic question is now what to do about secretory diarrhea. First, it would be wise to control ingredient inclusion levels to minimize the amount of water secretion in the gut. To this end, avoiding high levels of sugars and excess minerals is a must, but quite often counterproductive and/or cost prohibitive. In this case, ingredients that tend to absorb water in the gut might be of some help. Such ingredients include several clays and fibers with a high water binding capacity.