Texas Equine Veterinary Association

www.texasequineva.com • 9 bioavailability of supplemental forms. Unfortunately, little work has been done in recent years determining the bioavailability of various forms of minerals for supplementation, particularly regarding calcium (Ca 2+ ) and magnesium (Mg 2+ ). While it is generally accepted that organic forms of minerals are more bioavailable than inorganic forms, this has not been well published and may not always hold true, especially in the case of macrominerals. Sodium (Na + ), potassium (K + ) and chloride (Cl - ) are most commonly supplemented in their salt forms (NaCl, KCl) with NaCl supplemented at twice the concentration of KCl. Many more supplemental forms exist for calcium (Ca 2+ ) and magnesium (Mg 2+ ), although little evidence exists on which is preferred. is is in part due to the fact that many studies investigating the effects of magnesium do not consider the competitive absorption of magnesium (Mg 2+ ) and calcium (Ca 2+ ) resulting in confounding effects making any conclusions drawn from those studies inappropriate. It is believed that natural forms of magnesium in a horse's normal diet (Mg 2+ ) have an absorption efficiency around 40-60%, which may be increased to 70% through supplementation forms of inorganic magnesium (Mg 2+ ) including magnesium oxide, magnesium sulfate, etc. ere are similar forms of calcium (Ca 2+ ) available, but the most common form of calcium supplementation is in the form of ground limestone, or calcium carbonate. e argument of organic vs inorganic mineral source has become a popular topic. While there are organic sources of both calcium (calcium gluconate) and magnesium (magnesium gluconate) available, they only slightly improve bioavailability. is, along with the elevated cost of organic sources oen does not support its use. is is not the same as with microminerals (Zn, Cu, Co, Mn, etc.) where organic forms are substantially more bioavailable than inorganic and very much worth the increase in cost. One of the most common questions by consumers and used as a marketing objective by supplement companies are concentration claims. Consumers always want the highest concentrations, but with regards to electrolytes, concentration play a less significant role than the ratios of electrolytes to one another. e highest concentrations do not matter if ratios are imbalanced. A basic rule of thumb is a 1:2:4 ratio of potassium (K + ), sodium (Na + ), and chloride (Cl - ). is ratio is easily maintained by formulating an electrolyte with twice the concentration of NaCl as KCl. Calcium (Ca 2+ ) and magnesium (Mg 2+ ) should be maintained in a 3:1 ratio in horses, which is different from that in many other monogastric species which is one reason why it is important to select an electrolyte specifically formulated for horses. Choosing an Electrolyte Replacement e most important factor when considering an electrolyte replacement is the ingredients list followed closely by the guaranteed analysis. e first ingredient in any supplemental electrolyte should be "salt." Unfortunately, many electrolyte supplements' first ingredient is dextrose. Dextrose is a sugar (disaccharide of glucose), not an electrolyte. While the dextrose will make the electrolyte supplement highly palatable, the objective is not to supplement sugar. Furthermore, salt (NaCl) is already highly palatable to horses, so the inclusion of dextrose is unnecessary. In the case of colic, diarrhea, or other gastrointestinal disturbances, the added sugar may actually contribute to further gastric upset, counteracting the beneficial effects of electrolytes. Finally, a quick review of the guaranteed analysis on the electrolyte label will assist in determining both the quality and potential effectiveness of the supplement. Rather than focusing solely on concentrations of individual ingredients, instead review the ratio of each active ingredient to confirm that electrolytes are in balance. For example, if minerals are listed independently (i.e., sodium, chloride, etc.), confirm the ratios are as described above at 1:2:4 potassium, sodium, chloride and 3:1 calcium to magnesium. If listed as ingredients (i.e., salt, KCl, etc.) ensure that salt (NaCl) and KCl are at a 2:1 ratio. is will provide greater information than simply reviewing concentration levels alone. Best Supplementation Practices Most horses will meet their electrolyte requirements through daily forage intake and free-choice access to a salt block. Horses undergoing moderate to intense exercise, or those with recent gastrointestinal disturbances may require additional supplementation. Feed companies account for this increased requirement of electrolytes associated with performance in commercially available performance feeds, but during periods of intense exercise, extreme heat/humidity, or reduced water consumption during a freeze, electrolyte supplementation may be warranted to encourage water consumption and replenishment of body fluids and electrolyte balance. When supplementing additional electrolytes, paste and top-dress options are ideal. A common trend is to add electrolytes to water to encourage water consumption and increase the palatability of the water source. While it may increase palatability of a water source, there is no way to monitor electrolyte consumption when added to water compared to top-dressing to feed or administering orally via a paste product. Monitoring electrolyte intake is crucial to monitoring water intake and ensuring the appropriate dose of electrolytes are consumed. Supplementing electrolytes is generally a safe practice with minimal risk of excess; however, the best supplementation of electrolytes is as-needed rather than a continual supplementation regimen if the horse is on a high-quality nutrition program. When giving as needed, simply recognize that oral supplementation of anything is not immediate and will take one to two hours for full effect. erefore, supplementing prior to an intense exercise bout may be a reasonable consideration. References Karp, G., J. Iwasa, and W. Marshall. 2015. Karp's Cell and Molecular biology: Concepts and Experiments. Wiley. 8th Ed.

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