Potassium, Sodium, and Chloride Deficiency - The Merck Veterinary Manual

Potassium, Sodium, and Chloride Deficiency

While requirements for potassium, sodium, and chloride have been clearly defined, it is also important to maintain a balance of electrolytes in the body. Often termed dietary electrolyte balance or acid-base balance, the effects of deficiency of any one element are often the consequence of alteration to this important balance as it affects osmoregulation.

Simple Deficiency:

A deficiency of chloride causes ataxia with classic signs of nervousness, often induced by sudden noise or fright. The main sign of hypokalemia is an overall muscle weakness characterized by weak extremities, poor intestinal tone with intestinal distention, cardiac weakness, and weakness and ultimately failure of the respiratory muscles. Hypokalemia is apt to occur during severe stress. Plasma protein is elevated, causing the kidney, under the influence of adrenocortical hormone, to discharge potassium into the urine. During adaptation to the stress, blood flow to the muscle gradually improves, and the muscle begins to retrieve lost potassium. As liver glycogen is restored, potassium returns to the liver. This may result in temporary prolongation of the hypokalemia. Effects of administering potassium salts to chickens during and following severe stress periods have not been adequately investigated.

When fed a diet low in protein and potassium or when starving, animals grow slowly but do not show a potassium deficiency. Potassium derived from metabolized tissue protein replaces that lost in the urine and lacking in the diet. Under such conditions, less potassium is needed. The ratio of potassium to nitrogen in urine is relatively constant and is the same as that found in fresh muscle. Thus, tissue nitrogen and potassium are released together from metabolized tissue.

A deficiency of sodium leads to a lowering of osmotic pressure and a change in acid-base balance in the body. Cardiac output and blood pressure fall, hematocrit increases, elasticity of subcutaneous tissues decreases, and adrenal function is impaired. This leads to an increase in blood uric acid levels, which can result in shock and death. A less severe sodium deficiency in chicks can result in retarded growth, soft bones, corneal keratinization, impaired food utilization, and a decrease in plasma volume. In layers, reduced egg production, poor growth, and cannibalism may be noted. A number of diseases can result in sodium depletion from the body (eg, GI losses from diarrhea or urinary losses from renal or adrenal damage).

Electrolyte Imbalance:

Most commonly, electrolyte balance is described by the simple formula of Na⁺+ K⁺ - Cl^- expressed as mEq/kg (or mEq/g) of diet. Generally, an overall diet balance of 250 mEq/kg is optimal for normal physiologic function. The primary role of electrolytes is to maintain body water and ionic balance. Thus, requirements for elements such as sodium, potassium, and chlorine cannot be considered individually, as it is the overall balance that is important. Electrolyte balance is affected by 3 factors, namely the balance and proportion of these electrolytes in the diet, endogenous acid production, and the rate of renal clearance.

In most situations, the body attempts to maintain the balance between cations and anions in the body such that physiologic pH is maintained. If conditions in the body result in a shift toward acid or base conditions, physiologic defense mechanisms alter metabolism to maintain normal pH. Actual electrolyte imbalances rarely occur because these regulatory mechanisms must ensure optimal cellular pH and osmolarity. Electrolyte balance can therefore more correctly be described as the mechanisms that must occur in the body to achieve normal physiologic pH.

Electrolyte imbalance causes a number of metabolic disorders in birds, most notably tibial dyschondroplasia and respiratory alkalosis in layers. Tibial dyschondroplasia in young broiler chickens can be effected by the electrolyte balance of the diet. The unusual development of the cartilage plug at the growth plate of the tibia can be induced by a number of factors, although its incidence can be greatly increased by metabolic acidosis induced by feeding products such as NH₄Cl. Tibial dyschondroplasia occurs more frequently when the diet contains an excess of sodium relative to potassium and a very high level of chloride.

Overall electrolyte balance is always important, but is most critical when chloride or sulfur levels are high. With low dietary chloride levels, there is often little response to the manipulation of electrolyte balance; however, when dietary chloride levels are high, making adjustments to the dietary cations is critical to maintain overall balance. Alternatively, chloride levels can be reduced, although chickens have requirements ~0.12-0.15% of the diet, and deficiency signs will develop with dietary levels <0.12%. Therefore, care must be taken to meet the minimum chloride requirements when, for example, NaHCO₃ replaces NaCl in a diet.