He further specifies that if a calf is depressed and refuses to nurse, one (and only one) feeding of milk can be withheld, and, in such a case, a high-osmolality (hypertonic) electrolyte product (osmolality between 400 and 600 mOsm/L) is required because it will provide higher energy levels to help replace lost milk. When milk is retained in the diet, particularly in beef calves or auto-fed calves that consume milk frequently, a lower-osmolality (isotonic) electrolyte (near 300 mOsm/L) is recommended. Smith says an osmolality of 600 mOsm/L is the greatest concentration at which intestinal villi can process the solution, so electrolytes with higher osmolality levels are not recommended.
Smith also discourages the use of oral electrolyte products containing psyllium as added fiber. “While it may produce a desirable change in the physical characteristics of feces, psyllium actually reduces calves’ energy levels and slows their recovery,” he says. Rice-based electrolyte products, he adds, are becoming a popular choice in human medicine. However, Smith cautions that such products cause severe diarrhea in calves because they lack a maltase enzyme needed to metabolize the glucose polymers they contain.
The importance of alkalinizing agents
Smith says it is absolutely essential that any oral electrolyte solution used in calves have an alkalinizing agent to correct metabolic acidosis. The three most common alkalinizing agents are bicarbonate, acetate and propionate.
Bicarbonate is the alkalinizing agent used almost exclusively in commercial oral electrolyte solutions in the United States, while acetate- and propionate-containing products are more widely available in Europe and Canada. Smith says that while all three components have similar alkalinizing ability, he prefers acetate and propionate over bicarbonate for a number of reasons:
- Acetate and propionate produce energy when metabolized; bicarbonate does not.
- Acetate and propionate stimulate sodium and water absorption in the intestine.
- Acetate and propionate inhibit the growth of Salmonella and other bacteria.
- Bicarbonate alkalinizes the abomasums.
The researcher notes that the higher pH levels created in the abomasum by bicarbonate increases the likelihood that bacteria such as E. coli and Salmonella will remain viable and reach the small intestine, thus potentially cultivating an environment for more detrimental pathogen growth and greater intensity and/or duration of scours. As an illustration of this phenomenon, Smith points to the fact that enterotoxigenic E. coli (ETEC) diarrhea has been repeatedly induced in calves older than 3 days of age, by feeding bicarbonate along with E. coli inoculation. ETEC diarrhea in its naturally occurring state typically only is observed in calves 1 to 3 days of age.