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Sodium (Na) in Powdered Milk Replacers



Dietary considerations


Sodium is another essential nutrient, as well as an electrolyte that works with potassium. Sodium plays a key role in controlling fluid balance and blood volume (and pressure).  It also affects muscle and nerve function. Most of the body’s sodium is located in the blood and fluids around the cells.


Sodium concentration imbalance


As sodium is a primary electrolyte, the effects of a sodium deficiency (hyponatraemia) can range from mild to life-threatening. It is almost always caused by dilution of total body sodium secondary to increases in total body water (water overload). Sometimes it is a result of depletion of total body sodium in excess of concurrent body water losses. This would be consistent with dehydration commonly seen during intake and stabilization of rehab animals, or cases of severe diarrhea.


The symptoms of hyponatraemia are related to both the severity and the rapidity of the fall in the plasma sodium concentration. Patients with mild hyponatraemia are usually asymptomatic. General weakness and lack of interest in food can occur as the deficiency increases. Lethargy, restlessness, and disorientation follow. With severe and rapidly evolving hyponatraemia, seizure, coma, permanent brain damage, respiratory arrest, and death may occur.


Milk replacer analysis


Sodium concentrations are shown below by product. The average value for all samples of each product is shown, as well as the range of high and low values for all of the samples for that product. Most of the products are supplemented by the inclusion of sodium chloride (commonly 'salt') as indicated on the package labeling. 


The general variability may be noteworthy in some products and should be considered in percentage terms. For example, Fox Valley 20/50, for the lots tested, has a range of +83% to -41% from its average concentration value. Another example is Esbilac® with a range of +61% to -42%.


Since the correct range of concentration values for all species are different, and since wild species milk composition is very limited, reference values for whole and lowfat dry milk are provided in the chart.

Sodium concentration chart.jpg

Since averages can at times be misleading, a closer look at a few of the products where multiple test values are available between time periods, can reveal how the concentration values may have changed over time. Then if those changes are significant, either increase or decrease, the reader may want to focus on the most recent profile of the product. 


Even though some of the changes reflected below may be significant over time, simply trying to adjust with supplements requires considerable knowledge and has the potential to worsen an adverse situation. Please review the section on mineral supplementation in the minerals overview.

Sodium changes.jpg

References and further reading (not intended as an exhaustive list)


Disorders of sodium balance. Rebecca M Reynolds, et al. British Medical Journal. 2006 Mar 25; 332(7543): 702–705.

doi: 10.1136/bmj.332.7543.702 .   PMCID: PMC1410848 .   PMID: 16565125

The information included on this website for dietary minerals is extremely narrow in its scope and nature. It is limited to certain charts and graphs displaying content values (% of total) of various powdered milk replacers as tested by an independent chemical lab. Extremely brief overview information is provided as to the primary nutritional and medical benefits of each mineral, as well as a limited discussion of issues that may arise from concentration levels in the body that may be considered deficit or toxic. Entire textbooks on dietary minerals are written for the medical and veterinary professions, in addition to the internet providing ready access to both scholarly and popular literature. Some of those references are included above.


The data values presented above only represent the test values for the presence and concentration of the mineral conducted according to standard chemical testing methods in a controlled laboratory setting. Any point test value is accompanied by a measurement uncertainty range of +/-20%. The concentration values are in no measure an indication of how much of the mineral may be provided to an animal in reconstituted formula or its bioavailability (its degree of digestibility, absorption, or ultimate utilization). Additionally, no testing was performed as to the source of the mineral in the product (such as inorganic salts) or the grade of any added supplements containing the mineral.


What the data can do is inform the reader as to (1) concentration levels in a product as most recently tested (2) changes over time and between lots, and (3) comparisons of relative concentration levels between products. It is merely data that may serve as a starting point when deciding on a milk replacer product(s) and a recipe, or information to consider if certain medical symptoms appear that could be a result of absence or excess of a specific mineral in the formula. The reader is encouraged to consult veterinary or nutritional professionals prior to providing additional supplementation of any mineral.

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