15 - Sodium and chlorine bioavailability

Abstract

The importance of dietary salt (NaCl) for animals was known for hundreds of years before the metabolic effects of the compound were studied scientifically. Sodium and chlorine along with potassium function to maintain osmotic pressure, acid‑base balance, and fluid balance in body tissues. Feed intake and growth have been used to assess the requirement or toxic level of sodium and/or chlorine for broiler chicks. Damron and colleagues supplemented sodium-deficient diets for broiler chicks with 196, 392, and 588 ppm added sodium as sodium chloride or sodium bicarbonate in one trial and the lower two added amounts as either source in a second trial. Growth was similar in broilers when fed sodium chloride or ammonium chloride, it only added to a chlorine-deficient diet. Availability of sodium in various phosphorus sources has been determined with broilers. Summers and Leeson reported that sodium availability was greater from canola meal than from soybean meal. Dietary sodium and chloride are highly available and freely absorbed. Fecal excretion is not an integral part of sodium or chlorine regulation in ruminants; thus, measurement of apparent absorption yields values very similar to those representing the true absorption. Decreasing ruminal pH decreased net transport of sodium and chlorine. Elevated dietary potassium decreased ruminal sodium concentration and absorption in sheep and steers. Sodium and chlorine have been supplied to animals for centuries in the form of common salt, sodium chloride. Sodium and chlorine in feedstuffs are considered to be well absorbed by animals. Apparent absorption of sodium from feedstuffs measured in cattle, sheep, swine, and horses ranged from about 70 to 95% with an average of 85% apparently absorbed.