Effect of dietary potassium on absorption of magnesium and other macroelements in sheep fed different levels of magnesium.

Two metabolism trials were conducted with 24 crossbred wether lambs. Two levels of Mg (.1 and .2%) and four levels of K (.6, 1.2, 2.4 and 4.8%) were fed in a 2 x 4 factorial arrangement of treatments. Each trial consisted of a 10-d preliminary period followed by a 10-d collection of feed, feces and urine. Increasing levels of dietary K resulted in a linear increase in fecal Mg excretion and a linear decrease in Mg absorption. A large depression in Mg absorption occurred when K was increased from 1.2 to 2.4% with a further decrease when K was increased to 4.8%. Lambs fed the high level of Mg (.2%) absorbed and retained more (P less than .05) total Mg (g/d, but not percentage of intake) compared with the low magnesium level (.1%). Dietary Mg did not affect the amount of K excreted, absorbed or retained. Increasing the level of dietary K resulted in a linear increase in urinary, fecal and total K excreted, absorbed and retained (P less than .05).